Ali, S. S. (2019). Problem-based learning: A student-centered approach. English Language Teaching, 12(5), 73-87.
Allan, D. (2004). Oxford placement test. Oxford University Press.
Ansarian, L., & Lin, T. M. (2018). Problem-based language learning and teaching an innovative approach to learn a new language. London: Springer.
Ansarian, L., Adlipour, A. A., Saber, M. A., & Shafiei, E. (2016). The impact of problem-based learning on Iranian EFL learners’ speaking proficiency. Advances in Language and Literary Studies, 7(3), 84-94. https://doi.org/10.7575/aiac.alls.v.7n.3p.84
Aryanti, N. W., & Artini, L. P. (2017). The impact of problem-based learning on productive skills and attitude toward English language learning. Advances in Social Science, Education and Humanities Research, 34(1), 15-20. https://doi.org/10.2991/icirad-17.2017.4
Astuti, D. A. (2017). The effectiveness of learning vocabulary in subtitle fable story using problem-based learning method. Teacher Training and Education, 1-10. University of PGRI.
Azer, S. (2004). Becoming a student in PBL course: Twelve tips for successful group discussion. Medical Teacher, 26(1), 12-15. https://doi.org/10.1080/0142159032000156533
Azman, N., & Shin, L. K. (2012). Problem-based learning in English for a second language classroom: Students’ perspectives. The International Journal of Learning: Annual Review, 18(6), 109-126.
Babaee, S., & Borji, H. V. (2017). The role of problem-based learning (PBL) e-portfolios on writing anxiety. International Journal of Sciences: Basic and Applied Research (IJSBAR), 36(1), 279-305.
Baresh, E. F., Ali, S. M., & Darmi, R. (2019). Using hybrid problem-based learning (HPBL) approach to enhance Libyan EFL students’ engagement with English language. International Journal of Education & Literacy Studies, 7(2), 9-20.
Barrell. (2007). Problem-based learning: An inquiry approach. US: Corwin Press.
Barrows, H. (2002). Is it truly possible to have such a thing as dPBL. Distance Education, 23(1), 119-122.
Berenji, S., Saeidi, M., & Ghafoori, N. (2020). Problem-based learning and its impact on EFL learners’ engagement and reading comprehension. Journal of Language Horizons, 4(1), 149-174.
Boonkit, K. (2010). Enhancing the development of speaking skills for non-native speakers of English. Procedia - Social and Behavioral Sciences, 2(2), 1305-1309.
Boothe, D., & Caspary, M. (2017). Multicultural problem-based learning approaches facilitate ESP language acquisition. International Journal of Learning, Teaching and Educational Research, 16(3), 1-14.
Bosco, F. M., Bucciarelli, M., & Bara, B. G. (2006). Recognition and repair of communicative failures: A developmental perspective. Journal of Pragmatics, 38(9), 1398-1429.
Brown, A., Iwashita, N., & McNamara, T. F. (2005). An examination of rater orientations and test taker performance on English for academic purposes speaking tasks. US: Educational Testing Service.
Burgess, J., & Spencer, S. (2000). Phonology and pronunciation in integrated language teaching and teacher education. System, 28(2), 191-215. https://doi.org/10.1016/S0346-251X(00)00007-5
Chai, Z. F., & Swanto, S. B. (2020). The effects of environmental problem-based learning method on Malaysian primary ESL learners’ vocabulary achievement. Indonesian TESOL Journal, 2(1), 59-70.
Chiou, B. (2019). The application of problem-based learning approach in English grammar instruction: A pilot study. Journal of Language Teaching and Research, 10(3), 446-453. http://doi.org/10.17507/jltr.1003.06
Cong-Lem, N. (2018). Web-based language learning (WBLL) for enhancing L2 speaking performance: A review. Advances in Language and Literary Studies, 9(4), 143-153.
Cummins, J. (2000). Putting language proficiency in its place: responding to critiques of the conversational/academic language distinction. In J. Cenoz & U. Jessner (EDs), English in europe: The acquisition of a third language (pp. 54-83). UK: Multilingual Matters.
Dahms, M. L., Spliid, C. M., & Nielsen, J. F. (2016). Teacher in a problem-based learning environment—Jack of all trades? European Journal of Engineering Education, 42(6), 1196-1219. https://doi.org/10.1080/03043797.2016.1271973
EhsaniFard, E., & Vakili, A. (2018). The effect of problem-based learning on Iranian EFL learners' vocabulary learning. The Journal of Asia TEFL, 15(1), 208-216.
Fahmi, R., Muslem, A., & Usman, B. (2021). The use of problem based learning to improve students’ speaking ability. English Education Journal (EEJ),12(2), 260-282.
Farmer, J. L., & Wilkinson, L. (2018). Engineering success: Using problem-based learning to develop critical thinking and communication skills. Proceedings of the Canadian Engineering Education Association (CEEA) Conference (pp. 3-6). Vancouver: Canadian Engineering Education Association (CEEA).
Gholami, M. J., Pishghadam, R., & Shayesteh, S. (2021). Emosensory competence, as an undisclosed construct of communicative competence, predicts L2 speaking ability. Journal of Research in Applied Linguistics, 12(1), 33-47. https://doi.org/10.22055/RALS.2021.16723
Golkova, D., & Hubackova, S. (2014). Productive skills in second language learning. Social and Behavioral Sciences 143(2014), 477-481.
Grice, P. (1989). Studies in the way of words. Harvard University Press.
Hairuddin, N. H., Machmoed, H. A., & R. R. (2018). The use of problem-based learning (PBL) method in teaching English writing. Scope of English Language Teaching, Literature and Linguistics, 1(1), 1-9.
Haryudin, A., & Syahrizal, T. (2018). Teaching English grammar using problem-based learning with puzzle at English education student of IKIP Siliwangi Bandung. Project, 1(1), 33-42.
Hashemian, M., & Farhang-Ju, M. (2018). Effects of metalinguistic feedback on grammatical accuracy of Iranian field (in)dependent L2 learners’ writing ability. Journal of Research in Applied Linguistics, 9(2), 141-161. https://doi.org/ 10.22055/rals.2018.13797
Humalda, D., & Zwaal, W. (2016). Problem-based learning in the first or second language: Does it make a difference? Research in Hospitality Management, 6(2), 207-211.
Husin, Z. (2007). Using problem-based learning (PBL) approach to promote ESL students’ vocabulary development. In A. Pandian, K. Y. Lie, P. Kell, & J. Serdang (Eds.), Innovation and intervention in ELT—Pathways & practice (pp. 358-371). University Putra Malaysia Press.
Iwashita, N., Brown, A., Mcnamara, T., & O’hagan, S. (2008). Assessed levels of second language speaking proficiency: How distinct?. Applied Linguistics, 29(1), 24-49.
Jaleniauskien, E. (2016). Revitalizing foreign language learning in higher education using a PBL curriculum. Procedia - Social and Behavioral Sciences, 232(2016), 265-275.
Kassem, M. A. (2018). Improving EFL students' speaking proficiency and motivation: A hybrid problem-based learning approach. Theory and Practice in Language Studies, 8(7), 848-859. http://doi.org/10.17507/tpls.0807.17
Keong, Y. C., & Mohammed, A. H. (2015). Improving Iraqi secondary students’ speaking performance through problem based learning approach. International Journal of Education and Research, 3(12), 87-96.
Kumar, R., & Refaei, B. (2017). Problem-based learning pedagogy fosters students’ critical thinking about writing. Interdisciplinary Journal of Problem-Based Learning, 11(2), 1-10. https://doi.org/10.7771/1541-5015.1670
Larmer, J. (2014). Project-based learning vs. problem-based learning vs. XBL. US: George Lucas Educational Foundation.
Lin, F. (2015). The impact of problem-based learning on Chinese-speaking elementary school students' English vocabulary learning and use. System, 55, 30-42.
Lin, L. F. (2017). Impacts of the problem-based learning pedagogy on English learners' reading comprehension, strategy use, and active learning attitudes. Journal of Education and Training Studies, 5(6), 109-125. https://doi.org/10.11114/jets.v5i6.2320
Lin, T. M., Ansarian, L., Tik, O. L., & Nair, A. B. (2019). The effects of problem-based language learning on the listening comprehension skills of Malaysian undergraduate students. The Journal of AsiaTEFL, 16(3), 996-1004. http://doi.org/10.18823/asiatefl.2019.16.3.16.996
Mohammadi, F. S. (2017). The effect of authentic problem-based vocabulary tasks on vocabulary learning of EFL learners. International Journal of Education & Literacy Studies, IJELS, 5(3), 35-40. http://doi.org/10.7575/aiac.ijels.v.5n.3p.35
Montafej, J., Lotfi, A. R., & Chalak, A. (2021). Implementation of hybrid and pure problem-based learning in EFL context: The case of speaking skill and self-confidence of Iranian undergraduate participants. International Journal of Foreign Language Teaching & Research, 9(35), 81-94.
Nilson, L. B. (2010). Teaching at its best: A research-based resource for college instructors. US: Jossey-Bass.
Noble, D. (2001). Digital diploma mills: The automation ofhigher education. US: Monthly Review Press.
Oliver, R., & Herrington, J. (2003). Exploring technology-mediated learning from a pedagogical perspective. Journal of Interactive Learning Environments, 11(2), 111-126.
Othman, N., & Shah, M. I. (2013). Problem-based learning in the English language classroom. English Language Teaching, 6(3), 125-135.
Pallant, J. (2016). SPSS survival manual. US: Allen & Unwin.
Payne, J. S. (2020). Developing L2 productive language skills online and the strategic use of instructional tools. Foreign Language Annals, 53(2), 243-249. https://doi.org/10.1111/flan.12457
Pohan, A. E. (2019). Problem-based learning; an efficient strategy on enhancing students' grammar ability. Anglo-Saxon, 10(1), 56-66.
Prancisca, S. (2016). The key to success: Building speaking competence through problem based learning (PBL) for real communication. Jurnal Visi Ilmu Pendidikan, 7(3), 1847-1858. http://doi.org/10.26418/jvip.v7i3.17180
Puspitasari, M. J. (2019). The implementation of problem based learning in teaching speaking analytical exposition text to eleventh grades. Retain, 7(4), 24-31.
Razavipour, K., Hoseini, F., & Validi, M. (2020). Washback to classroom climate: The case of an IELTS speaking preparation course. Journal of Research in Applied Linguistics, 11(1), 21-43. https://doi.org/10.22055/rals.2020.15415
Reeves, T. (2002). Storm clouds on the digital education horizon. In A. Williamson, C. Gunn, A. Young, & T. Clear (Eds.), Winds of Change in the Sea of Learning (pp. 17-26). Auckland, NZ: UNITEC Institute of Technology.
Roquet, H., & Pérez-Vidal, C. (2015). Do productive skills improve in content and language integrated learning contexts? The case of writing. Applied Linguistics, 38(4), 489-511. https://doi.org/10.1093/applin/amv050
Rotgans, J. I., & Schmidt, H. G. (2011). Cognitive engagement in the problem-based learning classroom. Advances in Health Sciences Education, 16(4), 465-479.
Salari, M., Zarifi, A., & Tarmizi, R. A. (2021). Effect of problem-based learning on communication skills of undergraduate nursing students. Journal of Clinical Care and Skills, 2(1), 21-27. http://doi.org/10.52547/jccs.2.1.21
Setyawana, D., Shofiyahb, A., Dimlantikac, T. I., Saktid, Y. T., & Susiloe, H. (2021). Implementation of problem-based learning model through lesson study on student communication skills. The 4th international conference on mathematics and science education (ICoMSE) (pp. 030012-030014). AIP Conference Proceedings 2330. https://doi.org/10.1063/5.0043165
Shamsan, B., & Syed, A. (2009). Evaluation of problem-based learning course at college of medicine, Qassim university, Saudi Arabia. Int J Health Sci (Qassim), 3(2), 249-258.
Sutrisna, G., & Artini, L. P. (2020). Does problem based learning affect students’ speaking skill and attitude toward ELL? Retorika: Jurnal Ilmu Bahasa, 6(2), 131-138. https://doi.org/10.22225/jr.6.2.2315.131-138
Syarafina, D. N., Jailani, & Winarni, R. (2018). The application of problem based learning to improve students’ self-efficacy. International Conference on Science and Applied Science (ICSAS) (pp. 1-8). Published by AIP Publishing. https://doi.org/10.1063/1.5054428
Tan, O. S. (2003). Problem-based learning innovation: Using problems to power learning in the 21st century. US: Thomson Learning.
Thornbury, S. (2005). How to teach speaking. US: Pearson Education ESL.
Ustũn, B. (2006). Communication skills training as part of a problem-based learning curriculum. Journal of Nursing Education, 45(10), 421-4. https://doi.org/10.3928/01484834-20061001-07
Uyeda, S., Madden, J., Brigham, L. A., Luft, J. A., & Washburne, J. (2002). Solving authentic science problems: Problem-based learning connects science to the world beyond school. The Science Teacher, 69(1), 24-29.
Weigand, E. (1998). Contrastive lexical semantics. In E. Weigand (Ed.), Contrastive lexical semantics (pp. 74-96). UK: John Benjamins Publishing Company.
Weiss, R. E. (2003). Designing problems to promote higher-order thinking. In D. S. Knowlton & D. C. Sharp (Eds.), Problem-based learning in the information age (pp. 25-31). US: Jossey-Bass.
Wilkins, D. (1972). Linguistics in language teaching. US: Arnold.
Woods, D. R., Hall, F. L., Eyles, C. H., & Hrymak, A. N. (1996). Tutored versus tutor-less groups in problem-based learning. American Journal of Pharmaceutical Education, 60, 231-238.
Zuhriyah, M. (2017). Problem-based learning to improve students' grammar competence. Language & Language Teaching Journals, 10(1), 48-61. https://doi.org/10.18326/rgt.v10i1.48-61