因應新冠肺炎疫情，許多第二語言教師開始正視利用線上學習資源以加強學生在課堂外的自我調控學習(self-regulated learning)。學生自主學習能力被認為是數位時代的關鍵能力之一，對獨立和終身學習起至關重要的作用。外語教師如何透過科技輔助第二語言學習，培養並提升學生自我調控學習能力成為重要議題。本研究主要探討高中生使用Duolingo App後，對自我調控學習能力之實現程度。其次探討運用Duolingo App作為第二語言輔助學習，外語學習焦慮對自我調控學習之影響。最後探究高中生在使用Duolingo App後，是否能增強應用Duolingo App學習第二語言的自我信心。

本研究以美國高中9-12年級184位，選修中文、日文或西班牙文的第二語言學習者為研究對象，進行為期八週的實驗。八週後收集Duolingo學生進度追踪數據以及問卷調查資料，隨後使用IBM SPSS 23.0 統計軟體及結構方程式VisualPLS 1.04b軟體進行量化研究分析。根據資料分析結果，（1）高中生使用Duolingo App作為第二語言輔助學習，學習者每週至少會抽出一天多的時間完成每週75點的目標點數。高中生使用Duolingo App後，自我調控學習能力屬於中等稍高水平。（2）外語學習焦慮對自我調控學習具負面影響，並且達到顯著水準。（3）高中生使用Duolingo App後，能增強應用Duolingo學習第二語言的自我信心。本研究結果提供語言應用軟體設計以及未來學術研究之參考。

In response to the COVID restrictions in school education, second language teachers have attempted to use online learning resources to enhance students' self-regulated learning outside the classroom. Student’s ability in self-regulated learning is one of the key competences in the digital age which plays a vital role towards independent and lifelong learning. It has become important for foreign language teachers to cultivate and improve students’ self-regulated learning ability through computer or mobile assisted language learning (CALL/ MALL). This study investigates the extent to which high school second language students can achieve self-regulated learning by utilizing the Duolingo App. The study further examines how foreign language learning anxiety affects self-regulated learning, and if students' self-confidence in learning a second language with Duolingo is enhanced after using the Duolingo App.

The participants comprised 184 American high school students enrolled in Chinese, Japanese, or Spanish who were tested during an eight-week period. Data was collected through the participants’ progress tracking records from Duolingo Classrooms and a survey for quantitative analysis. The findings were analyzed using IBM SPSS 23.0, and a model was examined with VisualPLS 1.04b Partial Least Squares Structural Equation Modeling.
The results showed that the participants spent at least one day a week to complete the target of 75 points a week. The survey results revealed the self-regulated learning level for the participants was at the moderate-to-high level. There is a negative and significant correlation between foreign language learning anxiety and self-regulated learning. There is a positive and significant correlation between self-regulated learning and self-confidence in second language learning.

參考文獻
一、中文文獻
（一）書籍類
林金錫、連育仁（2010）。華語文數位教學理論與實務。臺北市：新學林出版股份有限公司。
陳寬裕（2018）。結構方程模型分析實務：SPSS與SmartPLS的運用。臺北市：五南圖書出版有限股份公司。
謝天蔚（2007）。外語教學中的電腦運用：理論與實踐。California State University, Long Beach。
（二）期刊與雜誌類
林堂馨（2018）。自主學習的五大發展趨勢。教育研究月刊，295，126-145。
林麗娟（2011）。台灣國際學生學習華語數位資源之使用分析。圖書與資訊學刊，78，1-22。
陳姿青、張靜怡、李宜年（2007）。教育科技於華語教學之運用。明道通識論叢，2，179-202。
陳嘉怡（2017）。遠距跨國華語文教學-電腦媒介溝通學習成效因素研究。華文世界，120，63-75。
（三）其他研究報告或論文
何欣樺（2019）。探討在虛擬實境系統中實施任務教學法對華語文聽力及口說能力之研究。臺北市：國立臺灣師範大學碩士論文。
林玉涵（2017）。英語學習APP 輔助高職英語教學之研究。臺北市：國立台北科技大學碩士論文。
陳詠璇（2018）。中級華語學習者同步遠距教學互動之研究。臺北市：國立政治大學碩士論文。
（四）網路
中華民國僑務委員會。取自https://www.ocac.gov.tw/OCAC/Pages/VDetail.aspx?nodeid=1437&pid=7314
文英玲（2011）。從閱讀中學習-自主學習的理論和實踐。取自https://www.edb.gov.hk/attachment/tc/curriculum-development/kla/chi-edu/resources/primary/lang/020112011.ppt
全球華文網。取自https://www.huayuworld.org/index.php
許靜如（2012）。國際華語文學習網站發展分析Part II。數位典藏與學習電子報，11（9）。取自https://newsletter.teldap.tw/news/HaveYourSayContent.php?nid=5948&lid=687
張淑玲（2020）。面對停課挑戰，我們的「遠距學習」國家隊在哪裡？翻轉教育。取自https://flipedu.parenting.com.tw/article/5790
郭柏臣（2020）。科技輔助自主學習，教育部109年全國工作會議。取自https://etutor.moe.gov.tw/zh/sites/default/files/2020-01/109%E5%85%A8%E5%9C%8B%E5%B7%A5%E4%BD%9C%E6%9C%83%E8%AD%B0%20-%E6%95%99%E8%82%B2%E9%83%A8%E8%B3%87%E8%A8%8A%E5%8F%8A%E7%A7%91%E6%8A%80%E6%95%99%E8%82%B2%E5%8F%B8-%E9%83%AD%E4%BC%AF%E8%87%A3%E5%8F%B8%E9%95%B7-%E7%A7%91%E6%8A%80%E8%BC%94%E5%8A%A9%E8%87%AA%E4%B8%BB%E5%AD%B8%E7%BF%92.pdf
黃敦晴（2020）。駐美台灣媽媽第一手分享：美中學緊急停課，親師生如何無縫接軌學習？翻轉教育。取自https://flipedu.parenting.com.tw/article/5748 2020
Huang, E. (2017)。Duolingo 多鄰國免費語言學習 App 推出「日文學習」課程。取自https://www.playpcesor.com/2017/05/duolingo-app-japanese.html
Tang, K. (2019)。實用語言工具推薦，從零基礎開始學西班牙文，Duolingo實測心得介紹。取自https://blog.amazingtalker.com/zh-tw/zh-spa/%E8%A5%BF%E7%8F%AD%E7%89%99%E6%96%87%E5%AD%B8%E7%BF%92-duolingo%E5%AF%A6%E6%B8%AC%E5%BF%83%E5%BE%97%E4%BB%8B%E7%B4%B9/5932/

二、英文文獻
（一）書籍類
Beatty, K. (2003). Teaching and researching computer assisted language learning. London, England: Pearson Education Limited.
Benson, P. (2011). Teaching and researching: Autonomy in language learning (2nd ed.). New York and London: Routledge.
Brown, H. (2000). Personality factors. principles of language learning and teaching. New York: Pearson Education.
Chapelle, C. A., & Sauro S. (2017). The handbook of technology and second language teaching and learning. New Jersey: John Wiley & Sons.
Cohen, J. (1988). Statistical power analysis for the behavioral sciences. New York: Routledge.
Falk, R. F., & Miller, N. B. (1992). A primer for soft modeling. Akron, OH: University of Akron Press.
Kern, R., & Warschauer, M. (2000). Theory and practice of network-based language teaching. In M. Warschauer & R. Kern (Eds.), Network-based language teaching: Concepts and practice (pp. 1-19). New York: Cambridge University Press.
Kráľová, K., & Sorádová D. (2015). Foreign language learning anxiety. In Teaching foreign languages to learners with special educational needs (pp.91-100). DOI:10.17846/SEN. Nitra, Slovakia: Constantine the Philosopher University.
Krashen, S. D. (1981). Second language acquisition and second language learning. Oxford, UK: Pergamon Press Inc.
Kukulska-Hulme, A. (2018). Mobile-assisted language learning [Revised and updated version]. In C. A. Chapelle (Ed.), The concise encyclopedia of applied linguistics. New Jersey: Wiley.
Kukulska-Hulme, A. (2016). Mobile assistance in language learning: A critical appraisal (pp. 138–160). Beijing, China: China Central Radio & TV University Press Co., Ltd.
Levy M. (1997). CALL: Context and conceptualization. Oxford, UK: Oxford University Press.
Manso, M., Caeiro, M., & Llamas, M. (2014). Analysis of self-regulated learning strategies oriented to the design of software support. In Frontiers in education (FIE). Madrid, Spain: Aprobada. Pendiente de publicación.
Murray, J. H. (1997). Hamlet on the holodeck: The future of narrative in cyberspace. Cambridge, MA: Cambridge University Press.
Palalas, A. (2011). Mobile-assisted language learning: Designing for your students. In S. Thouësny & L. Bradley (Eds.), Second language teaching and learning with technology: Views of emergent researchers (pp. 71-94). Dublin: Research-publishing.net.
Paris, S.G., & Byrnes, J.P. (1989). The constructivist approach to self-regulation and learning in the classroom. In Self-regulated learning and academic achievement. theory, research, and practice (pp.169-200). New York: Springer-Verlag.
Pintrich, P. R. (2000). Chapter 14—The role of goal orientation in self-regulated learning. In M. Boekaerts, P. R. Pintrich, & M. Zeidner (Eds.), Handbook of self-regulation (pp. 451–502). Cambridge, MA: Academic Press. https://doi.org/10.1016/B978-012109890-2/50043-3
Skehan, P. (1989). Individual differences in second language learning. London: Edward Arnold.
Warschauer, M. (1996). Computer-assisted language learning: An introduction. In S. Fotos (Ed.), Multimedia language teaching (pp. 3-20). Tokyo, Japan: Logos International.
Warschauer, M. (2000). Technological change and the future of CALL. In S. Fotos & C. Brown (Eds.), New perspectives on CALLl for second and foreign language classrooms (pp. 15-25). Mahwah, NJ: Lawrence Erlbaum Associates.
Weiner, I. B., & Craighead, W. E. (Eds) (2010). The Corsini encyclopedia of psychology (Vol 3, 4th edition). New Jersey: John Wiley & Sons, Inc.
Zimmerman, B. J. (2000). Attaining self-regulation: A social cognitive perspective. In M. Boekaerts, P. R. Pintrich, & M. Zeidner (Eds.), Handbook of self-regulation (pp. 13-40). San Diego, California: Academic Press.
Zimmerman, B. J., & Moylan, A. R. (2009). Self-regulation: Where metacognition and motivation intersect. In D. J. Hacker, J. Dunlosky, & A. C. Graesser (Eds.), Handbook of metacognition in education (pp. 299-315). New York: Routledge.
（二）期刊與雜誌類
Ahmed, H. B. E. (2016). Duolingo as a bilingual learning app: a case study. Arab World English Journal, 7 (2). DOI: https://dx.doi.org/10.24093/awej/vol7no2.17
Aida, Y. (1994). Examination of Horwitz, Horwitz, and Cope’s construct of foreign language anxiety: The case of students of Japanese. The Modern Language Journal, 78(2), 155–168. https://doi.org/10.1111/j.1540-4781.1994.tb02026.x
Al-Hebaish, S. M. (2012). The correlation between general self-confidence and academic achievement in the oral presentation course. Theory and Practice in Language Studies, 2(1), 60–65. https://doi.org/10.4304/tpls.2.1.60-65
Bax, S. (2003). CALL—past, present and future. System, 31. 13-28. DOI:10.1016/S0346-251X(02)00071-4
Boekaerts, M. (1996). Self-regulated learning at the junction of cognition and motivation. European Psychologist,1(2), 100-112. DOI:10.1027/1016-9040.1.2.100
El Sakka, S.(2016). Self-regulated strategy instruction for developing speaking proficiency and reducing speaking anxiety of Egyptian university students. English Language Teaching. 9(12). http://dx.doi.org/10.5539/elt.v9n12p22
Finardi, K. R., Leao, R. G., & Amorim, G. B. (2016). Mobile assisted language learning: Affordances and limitations of Duolingo. Education and Linguistics Research, 2(2), 48. https://doi.org/10.5296/elr.v2i2.9842
Gafni, R., Achituv, D. B., & Rachmani, G. J. (2017). Learning foreign languages using mobile applications. Journal of Information Technology Education: Research, 16, 301-317. Retrieved from http://www.informingscience.org/Publications/3855
García Botero, G., & Questier, F. (2016). What students think and what they actually do in a mobile assisted language learning context: New insights for self-directed language learning in higher education. In S. Papadima-Sophocleous, L. Bradley, & S. Thouësny (Eds.), CALL communities and culture – short papers from EUROCALL 2016 (pp. 150–154). https://doi.org/10.14705/rpnet.2016.eurocall2016.553
García Botero, G., Questier, F., & Zhu, C. (2019). Self-directed language learning in a mobile-assisted, out-of-class context: Do students walk the talk? Computer-Assisted Language Learning, 32(1–2), 71–97. https://doi.org/10.1080/09588221.2018.1485707
Gürler, İ. (2015). Correlation between self- confidence and speaking skill of English language teaching and English language and literature preparatory students. Current Research in Social Sciences, 1(2),14-19.
Hariry, N.A.E. (2015). Mobile phones as useful language learning tools. European Scientific Journal, 11(16), 298-317. https://core.ac.uk/download/pdf/236416191.pdf
Hayrettin, T. C. E. (2015). The relationship between self-confidence and learning Turkish as a foreign language. Educational Research and Reviews, 10(18), 2575–2589. https://doi.org/10.5897/ERR2015.2445
Hong, J.-C., Cheng, C.-L., Hwang, M.-Y., Lee, C.-K., & Chang, H.-Y. (2009). Assessing the educational values of digital games. Journal of Computer-Assisted Learning, 25(5), 423-437. https://doi.org/10.1111/j.1365-2729.2009.00319.x
Hong, J.-C., Hwang, M.-Y., Lu, C.-H., Cheng, C.-L., Lee, Y.-C., & Lin, C.-L. (2009). Playfulness-based design in educational games: a perspective on an evolutionary contest game. Interactive Learning Environments, 17(1), 15-35, DOI: 10.1080/10494820701483615
Hong, J.-C., Hwang, M.-Y., Tai, K.-H., & Ye, J.-H. (2019). Raising insects with an application to enhance students’ self-confidence in interacting with insects. Interactive Learning Environments, 1–18. https://doi.org/10.1080/10494820.2019.1687524
Horwitz, E. (2001). Language anxiety and achievement. Annual Review of Applied Linguistics, 21, 112–126. https://doi.org/10.1017/S0267190501000071
Horwitz, E. K., Horwitz, M. B., & Cope, J. (1986). Foreign language classroom anxiety. The Modern Language Journal, 70(2), 125-132. http://dx.doi.org/10.1111/j.1540-4781.1986.tb05256.x
Kacetl, J., & Klímová, B. (2019). Use of smartphone applications in English language learning—a challenge for foreign language education. Education Sciences, 9(3), 179. https://doi.org/10.3390/educsci9030179
Kannan, J., & Munday, P. (2018). New trends in second language learning and teaching through the lens of ICT, networked learning, and artificial intelligence. Círculo de Lingüística Aplicada a La Comunicación, 76(0), 13–30. https://doi.org/10.5209/CLAC.62495
Klimova, B. (2020). Benefits of the use of mobile applications for learning a foreign language by elderly population. Procedia Computer Science, 176, 2184–2191. https://doi.org/10.1016/j.procs.2020.09.255
Liu, M., & Jackson, J. (2008). An exploration of Chinese EFL learners’ unwillingness to communicate and foreign language anxiety. The Modern Language Journal,92(1), 71-86.
Lucas, R. I., Miraflores, E., & Go, D. (2011). English language learning anxiety among foreign language learners in the Philippines. Philippine ESL Journal, 7, 84-119.
Maclntyre, P. D., & Gardner, R. C. (1994). The subtle effects of language anxiety on cognitive processing in the second language. Language Learning, 44(2), 283-306. http://dx.doi.org/10.1111/j.1467-1770.1994.tb01103.x
Marcos-Llinás, M., & Juan-Garau, M. (2009). Effects of language anxiety on three proficiency‐level courses of Spanish as a foreign language. Foreign Language Annals, 42, 94–111. https://doi.org/10.1111/j.1944-9720.2009.01010.x
Martirossian, A., & Hartoonian, A. (2015). Lowering foreign language anxiety through self-regulated learning strategy use. English Language Teaching, 8(12), 209. https://doi.org/10.5539/elt.v8n12p209
Miangah, T. M., & Nezarat, A. (2012). Mobile-assisted language learning. International Journal of Distributed and Parallel Systems, 3(1), 309–319. https://doi.org/10.5121/ijdps.2012.3126
Munday, P. (2015). The case for using Duolingo as part of the language classroom experience. Ried. Revista Iberoamericana de Educación a Distancia, 19(1). https://doi.org/10.5944/ried.19.1.14581
Ozer, O., & Kılıç, F. (2018). The effect of mobile-assisted language learning environment on EFL students’ academic achievement, cognitive load and acceptance of mobile learning tools. EURASIA Journal of Mathematics, Science and Technology Education, 14(7). https://doi.org/10.29333/ejmste/90992
Peters, K. (2007). M-learning: Positioning educators for a mobile, connected future. The International Review of Research in Open and Distributed Learning, 8(2). https://doi.org/10.19173/irrodl.v8i2.350
Pierce, J. L., Gardner, D. G., Cummings, L. L., & Dunham, R. B. (1989). Organization-based self-esteem: Construct definition measurement and validation. Academy of Management Journal, 32, 622–648.
Rodríguez-Arancón, P., Arús, J., & Calle, C. (2013). The use of current mobile learning applications in EFL. Procedia - Social and Behavioral Sciences, 103, 1189–1196. https://doi.org/10.1016/j.sbspro.2013.10.446
Rowe, F. A., & Rafferty, J. A. (2013). Instructional design interventions for supporting self-regulated learning: Outcomes in postsecondary e-learning environments. MERLOT Journal of Online Learning and Teaching, 9(4), 590-601.
Sahdan, S.B., & Abidin, N.A.B.Z. (2017). Self-regulated learning: A literature review for 21st century learning technology. Advanced Science Letters, 23(2), 912-915. https://doi.org/10.1166/asl.2017.7435
Saks, K., & Leijen, Ä. (2014). Distinguishing self-directed and self-regulated learning and measuring them in the e-learning context. Procedia Social and Behavioral Sciences, 112,190-198. https://doi.org/10.1016/j.sbspro.2014.01.1155
Sar, A.H., Avcu, R., & Isiklar, A. (2010). Analyzing undergraduate students’ self confidence levels in terms of some variables. Procedia Social and Behavioral Sciences 5, 1205–1209.
Sawilowsky, S. (2009). New effect size rules of thumb. Journal of Modern Applied Statistical Methods. 8 (2): 467–474. doi:10.22237/jmasm/1257035100
Shadiev, R., Liu, T., & Hwang, W. (2020). Review of research on mobile‐assisted language learning in familiar, authentic environments. British Journal of Educational Technology, 51(3), 709–720. https://doi.org/10.1111/bjet.12839
Shi, Z., Luo, G., & He, L. (2017). Mobile-assisted language learning using WeChat instant messaging. International Journal of Emerging Technologies in Learning (IJET), 12(02), 16–26.
Stockwell, G. (2013). Tracking learner usage of mobile phones for language learning outside of the classroom. CALICO Journal, 30, 118-136.
Tallon, M. (2009). Foreign language anxiety and heritage students of Spanish: A quantitative study. Foreign Language Annals, 42(1), 112-137
Vealey, R. S. (1986). Conceptualization of sport confidence and competitive orientation: Preliminary investigation and instrument development. Journal of Sport Psychology, 8, 221-246.
Viberg, O., Wasson, B., & Kukulska-Hulme, A. (2020). Mobile-assisted language learning through learning analytics for self-regulated learning (MALLAS): A conceptual framework. Australasian Journal of Educational Technology, 36(6), 34-52. https://doi.org/10.14742/ajet.6494
Zimmerman, B. J. (2002). Becoming a self-regulated learner: An overview. Theory Into Practice, 41(2), 64–70. https://doi.org/10.1207/s15430421tip4102_2
Zimmerman, B. J. (2008). Investigating self-regulation and motivation: Historical background, methodological developments, and future prospects. American Educational Research Journal, 45(1), 166-183.
Zimmerman, B. J., & Martinez-Pons, M. (1986). Development of a structured interview for assessing student use of self-regulated learning strategies. American Educational Research Journal, 23, 614-628. https://doi.org/10.3102/00028312023004614
Zimmerman, B. J., & Martinez-Pons, M. (1990). Student differences in self-regulated learning: Relating grade, sex, and giftedness to self-efficacy and strategy use. Journal of Educational Psychology, 82(1), 51–59. https://doi.org/10.1037/0022-0663.82.1.51
（三）其他研究報告或論文
Blanco, R.M., & Florez, L.P. (2019). Using the Duolingo app to enhance student self-regulation: A case study of a1 group developing self-monitoring strategy through mobile learning. University of Norte, Colombia. Retrieved from http://manglar.uninorte.edu.co/bitstream/handle/10584/8630/137540.pdf?sequence
Coe, R. (2002). It's the effect size, stupid: What effect size is and why it is important. Paper presented at the Annual Conference of the British Educational Research Association, University of Exeter, England.
Davies, G., Walker, R., Rendall, H., & Hewer, S. (2011). Introduction to new technologies and how they can contribute to language learning and teaching (CALL). Module 1.1 in Davies G. (ed.) Information and Communications Technology for Language Teachers (ICT4LT), Slough, Thames Valley University [Online]: http://www.ict4lt.org/en/en_mod1-1.htm
Euis, S., Kusmawan, U., & Patras, E. (2020). Relationship of emotional intelligent and self-confidence with students' self-regulated learning. Paper presented at the Conference of International Conference on Innovation in Education and Pedagogy (ICIEP) 2020, Indonesia.
Fitriyani (2018). Analyzing Duolingo as computer-assisted language learning (CALL) in as-sisting language autonomous learner. State Institute For Islamic Studies (IAIN). Salati-ga, Indonesia.
Harris, S. (2009). The relationship between self-esteem and academic success among African American students in the minority engineering program at a research extensive university in the southern portion of the United States. Doctoral Dissertation. Louisiana State University
Park, H., & Lee, A. (2006). L2 learners anxiety self confidence and oral performance. Kunsan National University and Concordia University. Retrieved from: http://www.paaljapan.org/resources/proceedings/PAAL10/pdfs/hyesook.pdf
Richard, M. (2016). Building virtual learning communities: A qualitative study of an online community of practice on the language-learning website Duolingo. University of Oulu, Finland.
Sharples, M., Taylor, J., & Vavoula, G. (2005). Towards a theory of mobile learning. Mobile technology: The future of learning in your hands. Mlearn 2005 Conference Proceedings. Cape Town, South Africa
Skinner, B. R. (2013). The relationship between confidence and performance throughout a competitive season. All graduate plan B and other reports. 285. Utah State University. https://digitalcommons.usu.edu/gradreports/285
Triquet, K., Peeters, J., & Lombaerts, K. (2017). Self-regulated learning online: benefits, empirical foundations, multi-level, and multi-modal promotion & evaluation thereof for teacher professional development. Contributing SRL Part to Teach-UP. A policy experimentation co-funded by Erasmus+. Deliverable D1.1: Gaps in ITE and CPD provision report. Department of Educational Sciences, Vrije Universiteit Brussel.
Tsai, C. (2016). The role of Duolingo in foreign language learners’ autonomous learning. The Asian Conference of Language Learning 2016, Taipei, Taiwan.
Vesselinov, R., & Grego, J. (2012). Duolingo effectiveness study. City University of New York & University of South Carolina, USA.
Zhang, X. (2018). Exploration of using MALL to help English learners in China overcome foreign language anxiety and improve their English communicative competence. University of Alberta, Canada.
（四）網路
ACTFL proficiency guidelines. Retrieved from https://www.actfl.org/resources/actfl-proficiency-guidelines-2012
Ahn, V. L. (2011). Duolingo - the next chapter in human computation, TEDxCMU 2011. Retrieved from: https://www.youtube.com/watch?v=cQl6jUjFjp4
Best apps for learning mandarin Chinese: We’ve tried them. Retrieved from https://www.alllanguageresources.com/best-apps-learn-chinese/
Blanco, C., & Reidler, V. (2020). Educator and parent guide: Making the most out of staying at home. Retrieved from: https://blog.duolingo.com/educator-and-parent-guide-making-the-most-out-of-staying-at-home/
Burgess, S., & Sievertsen, H. H. (2020). Schools, skills, and learning: The impact of COVID-19 on education. Retrieved from VoxEU.org website: https://voxeu.org/article/impact-covid-19-education
DoDEA world language standards. Retrieved from https://www.dodea.edu/Curriculum/foreignLanguage/upload/CCRS-WL-FINAL-web_quality.pdf
Duolingo guide for leaders in education. Retrieved from: https://duolingo-data.s3.amazonaws.com/s3/schools/active/Duolingo_for_Schools_Guide.pdf
Duolingo website. Retrieved from: https://www.duolingo.com/
Duolingo Schools website. Retrieved from: https://schools.duolingo.com/
Google Play store. Retrieved from: https://play.google.com/store/apps/details?id=com.hellochinese
O’Conor, L. (2014). Duolingo creator: 'I wanted to create a way to learn languages for free.' Education. The Guardian. Retrieved from: https://www.theguardian.com/education/2014/aug/27/luis-von-ahn-ceo-duolingo-interview
Pew research center internet, technology. Retrieved from: https://www.pewresearch.org/internet/fact-sheet/mobile/
UNESCO: Covid-19 school closures around the world will hit girls hardest. Retrieved from: https://en.unesco.org/news/covid-19-school-closures-around-world-will-hit-girls-hardest
Wolcott, M. (2008). What is web 2.0? Retrieved from: https://www.cbsnews.com/news/what-is-web-20/