INVESTIGATING THE IMPACT OF PEER FFEDBACK AND TEACHER FEEDBACK USING GOOGLE DOCS ON EFL STUDENTS’ WRITING PERFORMANCE

Online written corrective feedback via Google Docs, in recent years, has been used and brought about positive outcomes in different teaching contexts. In this light, this study was conducted to examine the different effects between teacher feedback using Google Docs and the combined peer feedback and teacher feedback using Google Docs on EFL high school students’ performance in writing paragraphs. The study also attempted to gain insights into students’ attitudes towards the effect of peer feedback and teacher feedback using Google Docs on their paragraph writing. In this study, a mixed research method was employed; both quantitative and qualitative data were collected. Twenty two grade 11 students in a high school in the Mekong Delta of Vietnam were selected as participants. They were assigned to two groups of treatment: the experimental group, receiving both peer feedback and teacher feedback using Google Docs and the control group who only received teacher feedback using Google Docs. Participants completed two writing tasks; each of them included first draft, second draft and final draft. Prior to the study, students from the experimental group received a face-to-face training on giving peer feedback. Data were collected from six drafts of two writing tasks, three drafts for one task, and interviews at the end of the study. Results indicated that participants who received teacher feedback in the control group performed their paragraph writing better than those receiving both peer feedback and teacher feedback using Google Docs in the experimental group after the study. Also, participants in both groups improved their writing performance in their revised drafts. From the interviews, results showed participants’ positive attitudes towards the impact of peer feedback and teacher feedback using Google Docs on their paragraph writing.   Article visualizations:

On the other hand, Lantolf (2004), as a follower of socio-cultural theory by Vygotsky (1978), indicated that the physical and psychological tools and artifacts possibly affect language development. Besides, viewed as a socio-culturally mediated process, Google Docs, a free web-based version of Microsoft word provided by Google, a platform for language learning (Fauziah & Sudarmaji, 2020;Oxnevad, 2013;Suwantarathip & Wichadee, 2014) has been used by a large number of learners for learning beyond the classrooms. Most researchers agree that Google Docs has multiple typical features to enhance computer-based or mobile-assisted writing instruction that can be integrated in the field of L2 writing, specifically in terms of giving feedback.
Concerning the Vietnamese context, particularly in high schools, although attention to teaching and learning English as a foreign language as a whole and writing skills in particular have been captured, EFL writing teachers confront considerable challenges such as students' low level of English language proficiency, their low motivation of learning English, the exam-driven focus and "large" size classes (Tran, 2007), the neglect of process-based writing teaching approach (Tran & Le, 2018) and time pressure (Luu, 2010). Likewise, most teachers teaching English writing in the setting of this study reported that they have been facing class time constraints (2020, personal communication, February 2). As a matter of fact, each writing class lasts within forty five minutes; consequently, students have little time for revising, self-reflecting and redrafting in class, and receive little individual feedback from teacher on their writing. Thus, despite having learned English for years, most of them are reported to have difficulty in writing in English and be low-achievers of English proficiency.
In such a context, it is therefore essential to conduct an experimental research testing the different effects between teacher feedback using Google Docs only and the combined peer feedback and teacher feedback using Google Docs on high school students' performance in writing paragraph as well as exploring if their reactions to the impact of peer feedback and teacher feedback using Google Docs on their paragraph writing is positive.
The purpose of this study is to address the two following questions: 1) What are the different effects between teacher feedback using Google Docs only and the combined peer feedback and teacher feedback using Google Docs on high school students' performance in writing paragraph? 2) What are students' attitudes towards the effect of peer feedback and teacher feedback using Google Docs on their paragraph writing?

Teaching writing in EFL contexts
Students in EFL contexts have encountered several difficulties in acquiring this skill (Fauziah & Sudarmaji, 2020;Klimova, 2011;Lavin, 2019;Nguyen, 2008;Phuong & Nguyen, 2019;Rahmatunisa, 2014); Srichanyachon, 2012;Tran & Le, 2018). Consequently, teaching writing has raised great concerns in different settings. In Indonesian context, Rahmatunisa (2014) reported that university students are not in favor of writing because when performing writing tasks, they faced several problems such as linguistics, cognitive (paragraph organization and text structure) and psychological problems (moods and difficulty to start writing). This is similar to Fauziah and Sudarmaji (2020)'s study, Indonesian university students in their study faced difficulties in writing a text due to five main problems in relation to the lack of vocabulary, difficulties in expressing ideas through written words, the grammatical errors, the lack of mastery of part of speech and the monotonous and traditional teaching method. Likewise, in higher education in Thai settings, the dominant cause of student's difficulty in developing writing skill is due to the "large" class sizes and the different English background knowledge of students in a class (Srichanyachon, 2012). Teaching academic writing to university students in Japan also poses a major challenge because students are considered having problems at the sentence level since they make too many errors in writing (Lavin, 2019). In Crezh republic, Klimova (2011) expressed that writing is reported to be the most difficult and the least attractive to learn; additionally, as it requires a lot of time and sensitive feedback, teachers also find it the most demanding skill to teach.
To a similar extent, teaching writing in Vietnam confronted similar considerable challenges. Nguyen (2008) echoed that a large number of EFL teachers in Vietnam, in general, find writing a complicated skill to teach, which may affect students' learning outcomes. The researchers also highlighted the problems of teaching EFL writing which focused more on the responsibility of teachers. Regarding Vietnamese high school contexts, Tran (2007) reported that teaching and learning L2 writing is a challenging task owing to students' low level of English language proficiency, their low motivation of learning English, the exam-driven focus and "large" class size. In addition, Tran and Le (2018) indicated that it is the product-based writing approach in use that challenges students in writing since their progress of writing is neglected. More importantly, students are reported to be deficient in terms of vocabulary and grammar, which may also hinder their success in creating good pieces of writing. Luu (2010) modified that time pressure is also the cause to students' ineffectiveness in writing in English. In summary, the difficulties and challenges posed in previous studies offer evidences to support the idea that it is necessary to seek a solution to the problems with respect to class time constraints, students' low achievement of English proficiency, and feedback on writing in "large" size class.

Online written corrective feedback
With the rapid development of computer technology, giving written corrective feedback via online platforms has drawn much attention from researchers in the field of EFL writing instruction (Ciftci & Kocoglu, 2012;Phuong & Nguyen, 2019;Suwantarathip & Wichadee, 2014). In this research theme, Ciftci and Kocoglu (2012) defined online written corrective feedback as a result from the advance of educational technologies and the increase in distance education courses in which students are able to be read online feedback provided by unseen virtual instructor, by their peers, or by the computer itself.
Likewise, Ene and Upton (2014) stated that technology-supported feedback, also known as e-feedback, refers to feedback that is communicated with the help of a technological tool. In the current study, online written corrective feedback consists of types of written feedback that a teacher gives to students' written paragraphs or one student gives to others' writing via an online application.
Giving online written corrective feedback was primarily conducted through the perspectives of sociocultural theory which was originally developed by Vygotsky (1978). Underlying this theoretical framework, based on Vygotsky's theories of development, language development is a socio-culturally mediated process which is affected by the physical and psychological tools and artifacts (Lantolf, 2004). In other words, it is possible for teachers to utilize online social platforms or online instructions to mediate their teaching practices. In addition, the construction of knowledge is not originated from the mind, but from the social interaction which is co-constructed between a more and a less knowledgeable individual. In this sense, the mediation provided by teacher functions as an instruction to help learners to move toward more independence and self-regulation in their learning. In this study, online written corrective feedback was explored from both teacher and students in the hope that the developmental level of students' writing skills may be enhanced.

Teacher feedback
Teacher feedback is a primary method that teachers use to respond to students' writings to assist their writing development (Hyland & Hyland, 2006;Srichanyachon, 2012). Also, teacher feedback is viewed as written comments or corrections given by teachers on all aspects of leaners' texts (Hyland & Hyland, 2006). According to Srichanyachon (2012), teacher feedback can serve as a powerful tool to boost students' motivation in the writing process in case it is done well. She added that writing teachers must give feedback in a polite way, which should not simply respond to students' writings with grammar and content focus but should include comments of praise and encouragement in their written feedback.
Apart from positive contributions of teacher feedback to writing instruction, this type of feedback is reported to bring about several negative effects on learners' writing. Yang et al. (2006) pointed out that although teachers are viewed as experts in the field of giving feedback, their feedback are sometimes misunderstood or misinterpreted by students. This was caused by "intellectual distance" between teachers and students. They echoed that this distance might be even larger in secondary education. In accordance with these claims, Wu (2006) supplemented that teacher feedback negatively affected Taiwanese L2 writers' revisions due to their low intermediate level of English proficiency. Hyland (2013) stated that the problem is that students themselves may understand teacher feedback in different ways depending on their background, their disciplines, their views of their teachers and their own abilities.
Accordingly, researchers in the field of written corrective feedback have been asked for increasing teacher feedback's effectiveness as well as minimizing students' misinterpretation about teacher feedback. Brookhart (2010) suggested that teachers should bear in mind that positive feedback is considered "positive reinforcement" while negative feedback is viewed as "punishment". Keh (1990) reported that comments such as "good" or "good point" were problematic because students pointed out that it was not clear whether a "good" was meant to compliment the content, writing style, or grammar. Moreover, one-word questions, for example, "Why?" were also full of problems because they did not provide enough information to complete the question successfully leaving the student no way of providing an appropriate answer. Accordingly, Keh (1990) developed a list of recommendations based on input from students for reference to write more effective comments: (1) link comments to lesson objectives (vocabulary, etc.); (2) note improvements: "good", and explain reasons why; (3) refer to a specific problem and provide strategy for revision; (4) write questions with enough information for students to answer; (5) write summative comment of strengths and weaknesses; (6) ask "honest" questions as a reader to a writer rather than statements which assume too much about the writer's intention/meaning. In brief, the researchers suggest ways of increasing teacher feedback's effectiveness as well as minimizing students' misinterpretation about teacher feedback on learners' writing. It is advisable for EFL teachers to take into account these recommendations, and have a specific plan for administering written corrective feedback to support learners during their writing revision.

Peer feedback
Peer feedback is a type of feedback that has drawn much attention from researchers in the field of language teaching and learning in recent years. It can be defined as the acquisition of knowledge and skills through active helping and supporting among learners who share equal status and matched companions (Topping, 2005). Hyland and Hyland (2006) stated that peer feedback can be regarded as a formative developmental process that provides the writers opportunities to discuss their texts as well as discover others' interpretations of them. In the current study, peer feedback is used as a kind of peer response in which students read each other's paragraph writings and give feedback on them.
In comparison with teacher feedback, peer feedback has been viewed as a useful source of feedback complementing teacher feedback (Rollinson, 2005;Topping, 1998). Nevertheless, in the majority of research that has compared teacher feedback with peer feedback (Tsui & Ng, 2000;Yang et al., 2006), students have been reported to be more in favor of teacher feedback than peer feedback. In spite of the fact, both types of feedback appear to be effective with different beneficial effects, and there are several advantages of using peer feedback. Gielen et al. (2010) indicated that peer feedback is seen as lesspower sensitive. What is more, peer feedback can help increase the social pressure on students to perform well on a task and their ability to understand feedback. It is also perceived as more understandable and quicker than teacher feedback. Yang et al. (2006) modified that peer feedback is beneficial in developing critical thinking, learner autonomy and social interaction among students.
Apart from that, there are a number of drawbacks of peer feedback activities. First, peer feedback mainly centers on surface errors or advice that does not help revision (Keh, 1990). To a similar extent, the quality of students' comments in EFL classrooms is reported to be insufficient due to their low achievement of language proficiency (Min, 2003). Also, Gielen et al. (2010) presented that peer judgments may partially correct, fully incorrect or misleading. Importantly, learners' intentions and provision of honest feedback may be influenced by "face saving" (Lin & Yang, 2011). Due to these problems, Min (2005) proposed that it is necessary to train students for giving peer feedback before they can participate in peer feedback activities because trained peer feedback might positively impact EFL students' revision types and quality of texts.
In short, well-trained peer feedback may increase the quality of students' feedback, so the use of peer feedback to support teacher in providing feedback on students' written texts can be potential. Regarding the process for providing peer feedback in EFL classrooms, Keh (1990) proposed that response may come earlier in the process with a focus on content, organization of ideas, development with examples, and peer editing nearing the final stages of drafting with a focus on grammar, punctuation, spelling and vocabulary use.

Google Docs
Google Docs is a free web-based version of Microsoft word provided by Google, which is mostly used for the purpose of learning beyond the classroom. Suwantarathip & Wichadee (2014) considered Google Docs as an online tool that provides teachers with different powerful features to help students develop writing skills. Oxnevad (2013) stated that Google Docs can be used by teachers to provide immediate feedback to the students. To a similar extent, Yang (2010) stated that a feature that differentiates Google Docs from other web 2.0 tools is that users can simultaneously edit the writing in the document and view the changes made by others if they are online at the same time.
In practice, writing teachers have used Google Docs for a number of reasons. First, Google Docs enables teachers to monitor students' progress. Teachers do not have to traditionally collect the students' drafts because of the fact that all the writing occurs online and drafts are saved on students' Gmail accounts (Kessler, Bikowski, & Boggs, 2012). Second, using Google Docs in the writing classroom lets learners determine their level of involvement (Franco, 2010). Besides, it promotes collaborative learning by the use of peer revision via Google Docs, which can be a powerful tool for improving student writing quality, and for changing the role of the writing teacher during revision (Semeraro & Moore, 2017). Here, they proposed that leaners should be provided with clear instructions on giving constructive feedback on others' written texts. Basing on the potential features of Google Docs from the literature, EFL teachers may consider using this tool in terms of creating writing activities beyond the classrooms.

Related studies 2.4.1. Possible effects of teacher feedback and peer feedback on learners' writing performance
In terms of giving written corrective feedback using paper, Chaudron (1984), Tsui and Ng (2000) and Yang et al. (2006) conducted their studies to investigate the effects of both teacher feedback and peer feedback on student writing. In Chaudron (1984)'s study, the researcher investigated the effects of feedback on English as a second language students' composition revision from advanced writing class and compared differences in L2 learners' improvement in revision of their English compositions depending on the method of evaluation, whether teacher comments, or peer evaluations. Twenty-three university students from two classes were selected as participants. Results from the study showed that neither teacher nor peer feedback was superior in promoting improvement on revision. In addition, results from the questionnaire indicated that students were consistently more positive about the feedback they would receive from native speakers, compared with foreign students. Tsui and Ng (2000) conducted a mixed-method research to examine the impact of teacher and peer comments on revisions in writing among secondary L2 learners in Hong Kong. Results from both quantitative and qualitative data showed that all students addressed a higher percentage of teacher feedback than peer feedback. They favored teacher comments and saw the teacher as a figure of authority that ensured quality while a larger of peer comments were dismissed due to its uselessness. The study also indicated four roles of peer comments that contributed positively to the writing process. Peer comments can enable writers to develop a sense of audience, raise their awareness of their own strengths and weaknesses, engage in collaborative learning and notice the ownership of their texts. Yang et al. (2006) compared the effects of peer feedback and teacher feedback in a Chinese EFL writing class. There were two groups of university students writing essays on the same topic in which one receiving feedback from the teacher and one from their peers. Textual and questionnaire data from both groups and video recordings and interviews from twelve individual students revealed that students used both teacher feedback and peer feedback to improve their writing, but teacher feedback was more likely to be incorporated and led to greater improvements in the writing than peer feedback. However, peer feedback appears to bring about a higher percentage of meaning-change revision whilst most teacher-influenced revisions occur at surface level. This could be explained because negotiation of meaning during the peer interaction helps to enhance mutual understanding, and reduce misinterpretation and miscommunication. The number of studies on the impact of online teacher feedback and peer feedback on student writing, from available literature, is still limited. In Wu's (2006) study, the researcher conducted an exploratory study to investigate EFL adult leaners' reactions to peer review and teacher feedback given and transmitted via the web to learners' blog in EFL composition class and to find out what effects online peer review have on the revisions of low-intermediate EFL writers as well as to see whether teacher feedback made significant effects on participants' revised drafts. Results showed that teacher feedback lead to both learners' positive and negative revisions, which was explained due to learners' attitude and their English proficiency. Meanwhile, the effects of peer feedback on student writing are unproductive. Although a larger number of peer review did not serve as meaningful and constructive comments, they were given as praise or blessings. To a similar extent, Ciftci and Kocoglu (2012) implemented an experimental study to investigate the effect of online peer feedback through blogs on Turkish EFL students' writing performance. Here, the control group (15 students, classroom-based) attended inclass writing activities; however, instead of using written corrective feedback, the researchers utilized face-to-face oral discussions for peer feedback. The experimental group (15 students, blog-based) attended classes in the computer laboratory and integrated blog peer feedback into their process oriented writing classes. The results revealed that the students in both the control and experimental group made improvement in their writing, particularly in their revised drafts. In addition, students held a positive attitude toward the use of blogs in writing classes as an effective writing and peer-editing platform. Ertmer et al. (2019) carried out a study to investigate the impact of peer feedback used as an instructional strategy to increase the quality of students' online postings and examine their perceptions of the value of the peer feedback process. Both quantitative and qualitative data were collected through participant interviews, scored ratings of students' weekly discussion postings, and responses to both entry and exit survey questionnaires. Results suggested that despite seeing no quantitative improvement in the quality of students' postings during the peer feedback process, interview data suggested that participants valued the peer feedback process and benefited from having to give and receive peer feedback. The process of peer feedback helps them reinforce their learning and achieve higher understanding. Phuong and Nguyen (2019) implemented an empirical research to explore the possible effects of peer feedback on Facebook on EFL high school students' writing performance. With the participation of 39 eleventh graders, 4 English teachers and a teacher researcher who are responsible for scoring writing papers, this study was designed to compare students' first drafts with final drafts of two writing topics. Results from students' questionnaires and interviews revealed that students' writing performance after the 12-week study was significantly enhanced and students had positive attitudes towards using Facebook as a means of peer feedback as well as learning English.
In terms of the combination of peer feedback and teacher feedback in writing classes, Tai et al. (2015) conducted an experimental study to compare the effects of the combination of teacher-led feedback and peer review (teacher feedback+ peer response) and a single teacher feedback method on the writing performance of EFL university students within a collaborative online learning system. Results revealed that the students in the teacher feedback + peer response group demonstrated greater improvements than INVESTIGATING THE IMPACT OF PEER FFEDBACK AND TEACHER FEEDBACK USING GOOGLE DOCS ON EFL STUDENTS' WRITING PERFORMANCE those who received only teacher feedback in terms of holistic writing skills and the subscales of content, organization, grammar, mechanics, and style. Ebadi and Rahimi (2017) implemented a quasi-experimental study to explore the impact of online peer-editing using Google Docs and peer-editing in a face-to-face classroom on EFL learners' academic writing skills. The participants are two intact classes, each with ten EFL learners. IELTS academic writing task 1 and task 2 were employed to assess the learners' academic writing skills, and a semi-structured interview was conducted to explore the learners' perceptions towards the impact of online peer-editing on academic writing skills. The results indicated that peer-editing both through using Google Docs and in the face-to-face classroom significantly developed the learners' academic writing skills, particularly on the four areas of academic writing including task achievement, coherence and cohesion, lexicon, and grammatical range and accuracy. Moreover, online peer-editing using Google Docs was more effective in developing EFL learners' academic writing, especially grammatical accuracy, in the long-term in comparison with peerediting in a face-to-face classroom. The results also showed that the learners had positive perceptions and thought that peer-editing using Google Docs was quite helpful to improve their academic writing skills. Neumann and Kopcha (2019) carried out a case study to investigate how the peerthen-teacher approach to peer review impact students' writing from a rural school. In the study, 21 participants (11 sixth grade; 10 seventh grade) wrote argumentative letters via Google Docs. There were two rounds of review for each letter. A peer provided feedback on the first draft, and the teacher provided feedback on the second draft. Results from their study revealed statistically significant changes because of both peer and teacher feedback in multiple areas of an argumentative writing rubric, which indicated that peerthen-teacher approach to revision can positively affect the writing achievement of middle school students. In particular, the mean scores increased from first to second draft after peer feedback in each rubric criterion; those differences were statistically significant in the area of Conventions. Likewise, the mean scores also increased from second to third draft after teacher feedback in each rubric criterion, especially in terms of Organization, Language and Vocabulary, and Conventions.

Possible effects of peer feedback and/or teacher feedback using Google Docs on learners' writing performance
Fauziah and Sudarmaji (2020) conducted a study to examine the effect of peerediting technique by using Google Docs on students' academic writing skills. As a true experiment with one group pre-test and post-test design, the study was conducted with the participation of 65 students during a semester. Results showed that the average score for the posttest was higher than that of the pre-test (71.40 and 55.69 respectively). This indicated that peer editing technique by using increased students' achievement in writing descriptive essay. In addition, the study also evaluated students' behavior during learning process with regard to teamwork, motivation, initiative, discipline, and active.
Results from the behavior assessment sheet revealed that students have discipline in learning process; however, they still lack initiative.

Learner's attitudes towards the impact of peer feedback and teacher feedback
using Google Docs on their writing Alharbi (2019) conducted a qualitative research to explore the potential of Google Docs in facilitating and supporting pedagogical practices in a writing course at a large Saudi university. Under a case study, the study was conducted among 10 EFL learners working in five pairs on article report writing over one academic semester. The instructor's observation and comments, learners' comments and text revisions through Google Docs, as well as their follow-up interviews were analyzed. The findings revealed students' positive views of Google Docs in support of writing instruction, specifically giving written corrective feedback.
Similarly, Diab (2019) revealed from his study that throughout the session training, students expressed their appreciation for receiving worth feedback using Google Docs from their peers and asserted that the process of giving comments to others during peer-editing was beneficial. The research showed that the comments and suggestions can be valuable for both the students giving the feedback and those receiving the feedback. Additionally, Google Docs developed their flexibility in writing as it provides the capacity to leave comments and suggestions in the margins of documents, allowing them to interact more quickly and conveniently than if they were writing on paper or other word-processing programs.
In terms of teacher feedback using Google Docs, Dathumma and Singhasiri (2015) conducted a study to investigate how students perceive teacher feedback on Google Docs. Results from six participants' interviews showed their positive attitudes towards giving feedback using Google Docs. Reasons for their satisfaction are also reported. For the most part, all of the participants agreed that they can easily notice the mistakes through the feedback using Google Docs. Moreover, it was useful in terms of the convenience of online accessibility; they could access to see the tasks with teacher feedback and receive them anywhere with the internet. Feedback using Google Docs could also be automatically saved, so it would be safe even if there were some technical problems.
From available literature, a wide range of previous studies were conducted on peer feedback using Google Docs, mostly for EFL university students. Also, none of research investigated into the effects of the combination of peer feedback and teacher feedback using Google Docs on EFL high school students' writing performance in the context of teaching and learning writing in Vietnam, particularly in the Mekong Delta. This means that the combined technique has drawn insufficient attention from researchers in the field. Hence, in this current study, the researchers would like to seek the potential impact of peer feedback and teacher feedback using Google Docs to support writing instruction and students' writing practices beyond classrooms.

Research design
This study was designed as a mixed methods research with the quan-qual model in which quantitative-then-qualitative data was collected. During this study, the implementation of peer feedback and teacher feedback using Google Docs-the independent variable-was monitored and students' paragraph writing performance-the dependent variable-was measured. After the experiment, participants' interviews were collected to gain insights into their attitudes towards the impact of peer feedback and teacher feedback using Google Docs on their paragraph writing.

Participants
The participants involved in the study were twenty two eleventh graders at a high school in the Mekong Delta in the academic year 2019-2020. They were assigned to two groups: the control group who received teacher feedback using Google Docs only and they experimental group receiving, both peer feedback and teacher feedback using Google Docs. Each group consists of 11 participants. Four from the experimental group and four from the control group participated in the interviews. Regarding their English proficiency in writing skill, results from the placement test showed that participants' mean score was 4.70 out of 10 in light of grading scale by the Ministry of Education and Training (2011) and its standard deviation is 1.71, which indicated that their writing performance was at the fair level, which ranges from 3.5 to 4.9. Two EFL high school teachers also involved in the study as raters grading students' written paragraphs. Both raters have more than eight-year experience teaching English in high schools.

Research instruments 3.3.1. Writing drafts a. Writing topics
During the implementation of peer feedback and teacher feedback using Google Docs, students completed two main writing tasks, which are developed from the topics of unit 13: Hobbies and unit 16: The Wonders of the World in English 11 textbooks (Hoang et al., 2007). According to Nguyen (2007), the number of words required for students to complete the tasks is between 120 and 130.

b. The analytic grading scale
An analytic rubric refers to an analysis of items involved in a piece of writing, which aims at assigning separate scores to each criterion and enables teachers to follow up students' progress (Klimova, 2011). More specific feedback is needed to evaluate students' proficiency levels for promotional purposes. Therefore, adapted from Reid (1993), the analytic grading scale was selected for marking writing drafts in this study. The scale was briefly presented as follows. In order to ensure the consistency of graded scores of students' written paragraphs, two English teachers were involved in the study as raters. Having read a hard copy of grading scale adapted from (Reid, 1993), both raters participated in an online video call via Zalo application before the study to discuss the grading scale of each component. During the call, the raters worked on scoring two paragraphs from participants' placement test as samples, one by one component. After that, both raters made an agreement on how to score each component of a writing draft as well as the total mark. Typically, one of the raters' agreements is that although students write paragraphs out of topic, they could earn one out of ten marks because their writings are in the right format. Moreover, the limited length of words in a paragraph could be at least 110, and students could get a maximum score in the component of Organization when their writing was wellorganized. Also, the grading scale of Grammar was evaluated based on the total number of errors in all sentences in a paragraph that a student made or the number of correct sentences he or she obtained. In general, both raters agreed that they would have a discussion in case there was any mismatch in each graded written paragraph so that the score was consistent during the study.

c. Peer feedback training
In this regard, adopted from Phuong and Nguyen (2019), guidelines for peer feedback concentrated on the following questions: 1) Is the text easy to understand? Do you enjoy the text? 2) What parts of the text do you find particularly interesting? 3) Are there main idea and supporting ideas in the text? 4) Is the information organized in a clear and logical way? 5) Are there any transitions (e.g. however, but, and, so, etc.)? What are they? Are they used in a good way? 6) Are there any parts that seems unclear or confusing to you? What are they? 7) Are there any errors in vocabulary, grammar, spelling, and verb tenses? What are they? How can you correct them? 8) Is there any information that needs to be expanded or added? 9) What should be done to improve the text? In this regard, students from the experimental group participated in a face-to-face training to provide peer feedback. At the training, students were introduced how to give peer feedback via Google Docs. Guided questions and useful language were also given to help them write peer feedback on the samples. The participants worked in small groups to practice giving peer feedback on two paragraphs as samples which are students' paragraphs from placement test. During the training, students were provided opportunities to raise questions to make sure that they are able to give constructive feedback on their peers' writings.

Interviews
Semi-structured interviews were used in this study in the form of face-to-face interviews with individual participants to collect more in-depth data on students' attitude towards the impact of peer feedback and teacher feedback using Google Docs to improve their writing. With the total of eight interviews, the students were allowed to utilize their native language instead of English to answer the questions to ensure that they had no difficulty in expressing their attitudes. Four students from each group were selected according to their highest or lowest mean score of all the drafts. This main source of data was analyzed and interpreted in order to triangulate findings of the study. Each interview lasted around forty minutes. All the interviews occurred at the English room of the school.

Data collection procedure and data analysis
The study employed both quantitative and qualitative data collection. The data was collected from March to June of the school year 2019-2020. Following was the procedure of data collection. • The researchers collected 26 consented forms involving participants' general information (name, age, present address, email address, their phone number and their experience of using Google Docs). • The researchers trained participants to write in English, share their writing and exchange feedback using Google Docs. • The researchers conducted sampling by using 40-minute placement test via Google Docs.
• Based on the results of the test, 22 participants were selected and assigned to two groups of treatment (the control group and the experimental group). • The researchers trained students from the experimental group to provide peer feedback; During the implementation, students labelled from student 1 to 11 were divided into 3 smaller groups: Group A, Group B and Group C. Each included 3-4 members. Their writings were put in one file, and students in the same sub-group provided peer feedback on each other's writings via Google Docs. The members of each sub-group was changed after the first writing topic. Week 3, 4, 5 • Students completed the first writing task, including first draft, second draft and final draft of the task.

Nguyen Thi Nien Hoa, Trinh Quoc Lap INVESTIGATING THE IMPACT OF PEER FFEDBACK AND TEACHER FEEDBACK USING GOOGLE DOCS ON EFL STUDENTS' WRITING PERFORMANCE
• Students in the control group received teacher feedback using Google Docs only in both their first drafts and second drafts; In particular, they received most indirect feedback under questions in their first drafts and direct feedback in their second drafts. • Students in the experimental group received peer feedback using Google Docs on their first drafts and teacher feedback on their second drafts. Here, most feedback from peers is praise or blessings in addition to spelling or grammatical correction. On their second drafts, students received both direct and indirect feedback from the teacher. Week 6, 7, 8 • Students completed the second writing task as the procedure of the first writing task; • Quantitative data was collected.
Week 11, 12, 13, 14 • Pilot interviews with two participants were conducted; Each of them represented their group; • The researchers conducted official interviews with the participation of eight students from both groups; • The interviews were carried out using Vietnamese in order to maximize students' expressions; • Excerpts from the participants' interviews were translated into English whereas the translated version was double checked. • The quantitative and qualitative collected data was documented, categorized and ready for the next stage of data analysis.
In the stage of data analysis, a number of tests were run on SPSS version 20 to analyze quantitative data from writing tasks. This study also employed thematic analysis to analyze qualitative data. The process of thematic analysis involves 6 steps: familiarizing with the data, generating initial codes, searching for themes, reviewing themes, defining and naming themes and producing the report (Braun & Clarke, 2006). The researchers at first printed English transcriptions of interviews out, read and re-read the handouts to familiarize with the data, then coded several repetitions that occur among respondents and search for themes. After the process of analysis, the results of themes were found in relation to four core aspects including Google Docs' supports, feedback using Google Docs, participants' difficulties and participants' suggestions for further studies.

The different effects between teacher feedback using Google Docs and the combined peer feedback and teacher feedback using Google Docs on participants' writing performance
To examine the effect of types of feedback using Google Docs which were used in the two groups of participants' writing performance, a Descriptive Statistics test was run to gain the results of writing performance between participants from the experimental group and those from the control group after the tasks. Next, Independent Samples T-tests were conducted to test the mean difference in writing performance between participants in the control group and those in the experimental group after the revised drafts of two writing tasks.  The results indicate that there is a significant difference in terms of writing performance between the experimental group and the control group after the two writing tasks. It can be concluded that participants who received teacher feedback using Google Docs only performed their paragraph writing better than those receiving the combined peer feedback and teacher feedback using Google Docs after the study. In this section, the writing performance between the control group and the experimental group were also compared in detail. Independent Samples T-tests were calculated on the mean scores of the components of the first drafts, the second drafts and final drafts of each writing topic between two groups of treatment to see the different effects of teacher feedback using Google Docs only and the combined peer feedback and teacher feedback using Google Docs on the two groups of participants' performance in writing paragraphs. As mentioned earlier, the scoring components of writ ing drafts consist of Topic sentence(s), Content, Organization, Vocabulary, Grammar, Use of transition and Concluding sentence(s). In both the first drafts and the second drafts, results from the tests show that there is no significant difference in all components between two groups (p > 0.08). Nonetheless, there is a statistically significant difference in the mean scores of Topic sentence(s) (p= 0.02 < 0.05), Content (p= 0.02 < 0.05) and Vocabulary (p=0.04 < 0.05) in the final draft between the control group and the experimental group while no difference is found in Organization, Grammar, Transition and Concluding sentence(s). Especially, the mean score in the component of Use of transition is completely similar (p=1.0). The results of the components of three writing drafts are presented in Table 4.  In spite of the differences, as can be observed from the table, results show that both groups of students' writing performance was greatly improved in terms of Organization, Vocabulary, Grammar and Use of transition after the revised drafts of the first writing topic. Similar to writing topic 1, Independent Samples T-tests were run on the scoring components of drafts of writing topic 2 in which students' writing performance in the experimental group was put in comparison to that in the control group. In all the drafts, results from the tests show that there is no significant difference in almost all components between two groups (p > 0.1). However, there is an exception in terms of Concluding sentence(s) in the first draft where there is a significant difference in the scores between two groups (p= 0.04 < 0.05). Specifically, the mean score of the experimental group (M= 0.31,SD= 0.19) is lower than that of the control group (M= 0.54,SD= 0.26). The results of the components of three writing drafts are presented in Table 5. As can be shown in Table 4, results indicate that both groups of students' writing performance was enhanced in almost all components of paragraph writing in terms of Topic sentence(s), Content, Organization, Vocabulary, Grammar and Concluding sentence(s) in the drafts of the second topic. Further exploration into the change of participants' writing performance after the study showed that in both groups there is a significant change for better in participants' writing performance after the two writing tasks. Results from the GLM tests indicated that after the study participants in both groups improved their performance in writing paragraphs.

Participants' attitudes towards the impact of peer feedback and teacher feedback using Google Docs on their writing performance
In order to gain more insights into the impact of peer feedback and teacher feedback using Google Docs only on their writing, the participants were encouraged to participate into individual semi-structured interviews with the researchers. Eight interviews were conducted. Four participants from the experimental group and four participants from the control group participated in the interviews. In general, participants expressed their positive attitudes towards the impact of peer feedback and teacher feedback using Google Docs on their writing. The results from thematic analysis were presented in detail below.

Google Docs' supports in participants' writing process and exchanging feedback
One of the major aspects of the interview data lean towards the use of Google Docs for writing English and exchanging feedback. Through their responses, eight out of eight students interviewed agreed that Google Docs is useful and convenient to their process of writing in English. The following were some reasons mentioned by the participants. First and foremost, the most common reason for preferring using Google Docs is because of its usefulness. This can be represented from Student 1 and 5's comments when they responded to the question "Do you think Google Docs can be used to write or learn English in general?" "…This application can be used for writing English because it is easy to compose and format texts, easily correct mistakes or edit directly in the writings. Besides that, we can use the app as a tool to learn English vocabulary, check English vocabulary. When words are written wrong, the app will report errors by highlighting and redlining the wrong words..." (Student 1) "…This application helps us improve our writing and reading skills, helps us recognize spelling mistakes. It can also be used to write or learn English because it helps me know a lot of vocabulary, know mistakes in writings and improve reading skills..." (Student 5) Student 1's remark indicated a strong opinion of the crucial help of Google Docs in improving the student writing. She explained that Google Docs, as a tool to learn English, has multi-functions as revising the texts easily, automatically showing typing errors or storing documents that are able to support writing. Meanwhile, Student 5 expressed a similar view in terms of helping her a lot learn English vocabulary and improve writing skills. In her remark, she also mentioned the development of reading skills as she experienced peer feedback from the experimental group, she had chances to read and comment on other students' writings, which could be explained why Google Docs can facilitate her in relation to improving reading skills. In addition to English writing kills, Student 1, 4 and 8 stated that Google Docs can also be useful in learning other subjects or self-studying. For example, Student 4 and 8 claimed that:

"…I know a useful learning application that helps me write better English, ... In addition, it is very convenient for preparing lessons; I can write on the app and send them [prepared lessons] to my teachers or friends…" (Student 4)
"…Google Docs can be used to learn to write in English… not only write in English, you can also write Literature on the app..." (Student 8) Likewise, Student 1 admitted also using Google Docs to prepare lessons for classes. Meanwhile, Student 1 preferred to copy good documents and save them on the app so that she could be used later. That is to say that she had an intention to use Google Docs to support her self-study later.
"…In addition, when finding good documents, they can be copied back to the app so as not to be lost…" (Student 1) Another typical reason for being in favor of using Google Docs is because of its convenience compared to paper English writing. A similar idea was also seen from Student 2, 5, 6 and 7. Underlying this opinion is the view of the convenient function of Google Docs that helps them recognize the spelling errors during writing. Furthermore, Student 7 and 8 expressed that their writings can be shared with others thanks to Google Docs, and Student 7 added that she could check the number of words she had written via Google Docs.
"…Google Docs is an application that integrates a lot of useful features such as sharing writings, checking users' spelling errors, checking the number of words written, ... to avoid rambling writing to help write the focal content…" (Student 7) In addition, Student 3 stated that Google Docs can be used offline instead online only. Out of eight participants' ideas, Student 1 claimed that Google Docs is a means of distance learning, and it is available on smart phones, which can be inferred that Google Docs can be used without charges.
"…Google Docs is a useful app for distance learning, available on phones ..." (Student 1) Besides the usefulness and convenience of Google Docs in relation to English writing, the interviewed participants stated that Google Docs can be also utilized for exchanging feedback. This is expressed by Student 1, 3, 4, 5, 6, 7 and 8. More importantly, they provided different reasons for this. For Student 4 and 5, they thought it was easy and convenient to give and receive feedback via Google Docs because the Google Docsbased comments were separated into smaller parts, making it easier for writers to understand the comments and edit writings than those on paper. For Student 1, 3, 6 and 7, they said that based on comments on Google Docs, they could directly correct the errors and edit their writing on the app instead of rewriting on paper. Student 6 also echoed that exchanging feedback via Google Docs did not require face-to-face meetings. On the contrary with other participants' views, Student 2 felt a little hard to receive feedback using Google Docs owing to her misunderstanding of feedback, which was further reported in the next section. In brief, almost all of the interviewed participants thought that Google Docs can be served as a useful and convenient application for exchanging feedback as well as English writing. This finding is consistent with what was found by previous studies (Alharbi, 2019;Dathumma & Singhasiri, 2015;Diab, 2019;Ebadi & Rahimi, 2017). As in this study, students thought that Google Docs supports writing process thanks to its usefulness and convenience. On top of that, it has multi-functions as editing the texts easily (Alharbi, 2019;Ebadi & Rahimi, 2017), automatically showing typing errors or noticing mistake by mistake within a text (Diab, 2019) and storing documents online (Dathumma & Singhasiri, 2015) that are able to make the process of writing easier and more convenient.

Feedback using Google Docs and the improvement of writing performance
Besides the investigation of Google Docs as a tool to support English writing, a great amount of the interview data hinges upon students' attitudes towards Google Docsbased feedback and its impact on their writing performance. Here, two types of feedback were involved in the interviews including teacher feedback and peer feedback. However, there were two groups of treatment, so while four students from the control group were asked about teacher feedback, the other four interviewed participants in the experimental group responded to both teacher feedback and peer feedback.
Regarding teacher feedback, from the interviews, all eight students from both groups considered this type of feedback useful to their writing revisions. Here, they shared similar viewpoints, and the extent of usefulness was various according to participants' expressions. Student 1, 2, 6 and 7 expressed that: "…I understand about 40-50% of teacher feedback and have to use Google Translate to understand all the comments. Because my level of English proficiency is not good, teacher feedback helps me understand and correct the errors in my writing ..." (Student 7) "… The comments from the teacher are useful because those help me to recognize errors when writing a paragraph, about errors in terms of grammar, organization in order to make the paragraph more complete. When correcting the errors directly through the teacher's suggestions, I remember them in the long term so that I can avoid them in the following writings. Besides, the teacher also suggests ways of arranging the sentences in a better organization so that they can convey information better ..." (Student 1) "…I think they are very useful because the comments from the teacher will make writing more complete ...." (Student 2) "…Teacher feedback is of course helpful because the feedback giver is the teacher who helps me correct the errors I make…" (Student 6) There is a fact that the usefulness of teacher feedback was highly evaluated by a majority of interviewed participants. Yet, all of them thought that the main purpose of teacher feedback was error correction, and teacher feedback would possibly focus on presenting students' errors or mistakes particularly on vocabulary and grammar; as a result, the quality of their writings may become higher. In addition, participants 1, 2, 3, and 7 expressed similar opinions on their misunderstanding of teacher feedback. They explained that they had to ask for help from Google Translate, an app of Google, to translate English into Vietnamese. For example, Student 2 said: "…every time I receive feedback, I have to use Google Translate to translate the parts that I do not understand into Vietnamese..." (Student 2) In terms of peer feedback, from four interviews, peer feedback was valued for its usefulness. This was expressed by four out of four participants. While Student 8 highly appreciated the impact of peer feedback on his writings because it helped him to modify missing ideas and the nature of peer feedback, according to his opinion, was quite comprehensible, Student 6 bluntly said that: Similar to Student 6's ideas, Student 7 echoed that peer feedback made better changes to her writings because it is useful in terms of lessening errors in her drafts and increasing the comprehensibility of writing. Nevertheless, out of four students, Student 5 thought that some feedback from peers were also not easy to understand, but they could learn from each other's writings though peer feedback in general.
In sum, nearly all the interviewed students perceived teacher feedback and peer feedback to be highly useful to their writing revisions as they expressed that based on feedback, they had opportunities to revise their drafts and made better changes to improve their writing quality. This finding is supported by Diab (2019), Ebadi &Rahimi (2017) andHedin (2012). In the current study, participants highly appreciated the convenience of giving and receiving feedback via Google Docs because the comments were separated into smaller parts, making it easier for writers to understand the feedback and edit writings than those on paper (Diab, 2019). Based on comments on Google Docs, they could directly correct the errors and edit their writing on the application instead of rewriting on paper; exchanging feedback via Google Docs did not require face-to-face meetings (Ebadi & Rahimi, 2017). Nevertheless, unlike some other earlier studies, this study did not explore students' attitudes towards teacher feedback using Google Docs compared to peer feedback using Google Docs. It revealed that students valued the usefulness of both teacher feedback and peer feedback. Results of the interviews also indicated that half of interviewed participants expressed similar opinions on their misunderstanding of teacher feedback. This finding is similar to that obtained by Gibbs et al. (2004), Higgins (2000) and Yang et al. (2006). Meanwhile, in line with what was found by Gielen et al. (2010), in this study, peer feedback was viewed as more comprehensible, and it can modify missing ideas and lessen errors in writing drafts.

Participants' difficulties during the experiment
During the interview sessions, all interviewed students except Student 4 were certain that they confronted several difficulties during the experiment. In this regard, there were three main areas of difficulty reported by the students namely writing task-related, technical-related and participant-related difficulty.
One of the typical difficulties that participants encountered is related to writing tasks. Participant 1, 2 and 7 echoed similar opinions on the fact that the length of words in paragraph writing should not be limited. Student 2 explained: "…when I finish writing, I have to cut out [delete] words to get sufficient number of words. For this reason, I feel that the writing is not as good as when I first wrote. I think criteria on word length should be omitted…" (Student 2) As a matter of technical-related difficulty, since students were expected to write English using Google Docs on their smart phones, they indicated that in order to have ideas, grammatical structures, vocabulary for their writing as well as understand teacher feedback and peer feedback, they used another app [Google Translate] at the same time, which made them thought that it took them a lot of time and inconvenienced them. This is expressed by Student 2 and 3.

"…I think it's a bit difficult because every time I receive feedback, I have to use Google Translate to translate parts that I don't understand into Vietnamese and after coming up with the answers, I have to again use it to translate them into English…" (Student 2)
"…I have encountered a problem. That is using different apps at the same time. Because there are many words, I don't understand their meanings, using Google Translate takes me a lot of time…" (Student 3) The last area of difficulty is related to the participants. As stated by Student 1 and 6, they indicated that they found it difficult during the process of writing due to their lack of knowledge of vocabulary and grammar as well as ideas for writing. For example, Student 6 expressed: Unfollowing the findings of other studies (Alharbi, 2019;Dathumma & Singhasiri, 2015) on the difficulties that students faced during the process of writing using Google Docs, including the slow internet connection and students' lack of necessary skill for using Google Docs, this study revealed that participants found it difficult to meet the required word length, as well as to use Translation application to understand the feedback and gain knowledge of vocabulary, grammar and ideas for writing. Due to these aforementioned problems, participants also provided suggestions for further studies.

Participants' suggestions
The last key aspect of the interview data centered on participants' suggestions for further studies. When being probed about how to help improve the effects of teacher feedback and peer feedback on their writing performance, seven out of eight students expressed their expectations in different aspects. In terms of teacher feedback, Student 1 proposed that the teacher should attach Vietnamese meaning to difficult words in order that students can get better understanding of teacher feedback. Moreover, teacher feedback should involve the detailed way of correcting errors as stated by Student 2. She said: "…I think the teacher should give suggestions on how to correct mistakes for students' references in order to produce better writing…" (Student 2) With respect to peer feedback, both Student 6 and 7 echoed similar opinions about students' attitude towards giving or receiving feedback. Student 6 stated that to improve the impact of peer feedback on writing, it is necessary for students to have a cooperative attitude in receiving feedback. She implied that when students ignore the comments, there will be no gains in their writing. What is more, students can create groups for study. Similar to Student 6's opinion, Student 8 stated that there should be interactive exchanges between peers to solve the problems in the feedback. Likewise, Student 7 added that students should give constructive comments on others' writing. She explained: "…students can give each other's feedback by commenting to help writers find mistakes to improve and complete [writing]…" (Student 7) She also suggested writing using Google Docs should be integrated with classroom activities. This was because it would help students write English better.
Another remarkable aspect of recommendations that participants mentioned during the interviews was in relation to writing topics/ tasks. As expressed by Student 3 and 7, writing topics should include more detailed prompts or questions which will be easier for them to avoid writing out of the topic. Student 8 modified that it would be better if there are different forms of writing instead paragraphs and the length of time for writing needed to be expanded. This idea is similar to Student 3's.
"… I think the teacher should give students different genres of writing instead paragraph; moreover, time for writing should be longer… (Student 8) Interestingly, eight out of eight students from the interviews expressed their strong beliefs on further practice. They believed that the more writing topics they practice on, the more their writing performance can be improved. They also provided reasons for that. A majority of students thought that when they write more writing topics on Google Docs, their knowledge of vocabulary and grammatical structures will be gradually improved and widened after single writing whilst Student 4 expressed that practicing writing more using Google Docs enabled her to revise what she had learned, which made her remember the knowledge in the long run. Similarly, Student 7 expressed her skills for analyzing the writing topic and searching vocabulary related to it will be upgraded as a result of writing more topics whereas Student 6 stated that writing more may gradually develop a writing habit for students.

Conclusion and recommendations
Results of the study indicated that students who received teacher feedback using Google Docs only had a better writing performance than those receiving the combined peer feedback and teacher feedback using Google Docs. Additionally, either the use of teacher feedback via Google Docs or the combined peer and teacher feedback positively impacted students' writing performance. From the interviews, the results showed participants' positive attitudes towards the effects of peer feedback and teacher feedback using Google Docs on their writing performance. Participants highly evaluated the usefulness of teacher feedback and peer feedback using Google Docs to help them improve their writing and thought that Google Docs could be served as a useful and convenient application for exchanging feedback in English writing.
Some implications for future implementation of peer feedback and teacher feedback using Google Docs are drawn. First, the results of the current study are grounded in existing evidence of the effectiveness of teacher feedback and peer feedback and the convenience of Google Docs for giving feedback to help foster students' writing. Accordingly, it is essential that EFL teachers should consider making use of Google Docs for peer feedback and teacher feedback to assist their writing instruction. Especially, those having problems with class time constraints and class "large" sizes may take into account the implementation of teacher feedback and peer feedback using Google Docs beyond the classrooms because of its potential effects on learner's writing performance. Second, the results contribute to the theory that teacher feedback makes more significant improvements on students' writing than peer feedback. In spite of that, results from the interviews showed students' misunderstanding of teacher feedback. In this sense, "intellectual distance" between teachers and students (Higgins, 2000;Gibbs et al., 2004;Yang et al., 2006) is taken into account. Hence, writing teachers should consider students' level of English proficiency when giving feedback on their texts. For instance, L1 meaning can be attached to difficult words in order that students can get better understanding of teacher feedback, and the detailed way of correcting errors should also be involved in comments. At this point, there should be interactive exchanges between teacher and students to solve the problems in the feedback and help enhance the students' comprehensibility of their texts. Third, while previous research focused on conducting peer feedback on university students, results of this study demonstrate that high school students still have an ability to practice on this type of feedback thanks to training sessions. Moreover, peer feedback together with teacher feedback may bring potential effects on students' writing revisions. Therefore, it is necessary to train students to provide constructive comments on others' writing in addition to compliments. Furthermore, it is highly recommended that teacher feedback and peer feedback should be combined and used in mixed-ability classes so that students' writing revisions may be optimized. Lastly, the findings should be taken into consideration when EFL writing teachers assign writing topics to students with different levels. Low level of English proficiency students need more detailed prompts or questions which will be easier for them to avoid writing out of the topic. More importantly, the word length of paragraph writing may be extended a bit so that students' ideas could be fully presented. Also, writing in English using Google Docs should be integrated with classroom activities to reinforce students' writing skills.
The research has obtained its aims. Yet, there were certain limitations. First, the duration of the quantitative data collection was conducted within eight weeks, so the longer-term effects of teacher feedback and peer feedback using Google Docs on students' writing performance have not been investigated. Second, the mixed-method nature of the study with limited number of participants hinders its results to be generalized to the whole EFL teaching context of Vietnam, or further, to other EFL teaching contexts. Besides that, in terms of teacher feedback using Google Docs, half of students in the interviews expressed that they found teacher feedback difficult to understand, which might affect their writing revisions as well as the extent of improvements in their writings. Lastly, the study suggests the positive impact of peer feedback training on the quality of peer feedback that led to the improvements of students' writing performance. Nevertheless, there is no investigation into to what extent students incorporated peer feedback into their revisions.
Based on the findings and the limitations of the research, several suggestions for future research should be observed. This study represents a preliminary attempt to explore the potential impact of peer feedback and teacher feedback using Google Docs on EFL high school students' writing performance. The findings of the study demonstrate that peer feedback and teacher feedback using Google Docs have potential benefits in teaching EFL writing. Therefore, it behooves other researchers in the field to replicate the same study and explore their effects on students' writing performance with a longer duration and a larger number of participants. Besides, while students in this study perceived teacher feedback as hard-to-understand, further studies are needed to establish a more interactive environment in which teacher and students can interact and deal with the problems in the feedback. Future research could also investigate the effects of Google Docs-based interactive and non-interactive teacher feedback on students' writing revisions. In addition to that, regarding the impact of peer feedback training on the quality of peer feedback, future research might focus offering a strong explicit instruction on how to give effective peer feedback so that students can help to enhance its benefits in terms of both comprehensibility and constructiveness.
In brief, Google Docs is a practical and convenient online application that can be used to assist EFL writing instruction. Compared to paper writing and other electric tools, Google Docs enabled students to be more flexible in writing, particularly in exchanging feedback. Remarkably, either peer feedback or teacher feedback using Google Docs positively affected students' writing revisions. It is evident that students recognized the usefulness and convenience of teacher feedback and peer feedback using Google Docs, and achieved significant improvements after the writing tasks. As the research was implemented at a high school context in the Mekong Delta of Vietnam, its findings are expected to foster the quality of teaching and learning EFL writing in Vietnam. It is therefore hoped that this experimental study gives stronger evidence of conducting peer and teacher feedback using Google Docs in teaching EFL writing in Vietnam as well as similar teaching contexts.