1. Bal, M. (2019). Use of digital games in writing education: An action research on gamification. Contemporary Educational Technology, 10(3), 246-271. https://doi.org/10.30935/cet.590005
2. Brinton, D. M. (2001). The use of media in language teaching. In M. Celce-Murcia (Ed.), Teaching English as a second or foreign language (pp. 459-475). Heinle and Heinle.
3. Dao, V. D. (2008). Some Vietnamese students’ problems with English grammar: A preliminary study. Hawaii Pacific University TESOL Working Paper Series, 6(2), 37-56.
4. Deterding, S., Dixon, D., Khaled, R., & Nacke, L. (2011). From game design elements to gamefulness: Defining gamification. In Proceedings of the 15th International Academic MindTrek Conference on Envisioning Future Media Environments–MindTrek’11 (pp. 9-15). https://doi.org/10.1145/2181037.2181040
5. Dewi, K. S., Myartawan, I. P. N. W., Swari, N. K. T. A., & Sugihartini, N. (2020). Quizizz effect on students’ grammar mastery in higher EFL classroom-based mobile assisted language. Language and Education Journal Undiksha, 3(1), 15-24.