Mulyadi Syahputra. “DUOLINGO GAMIFICATION: DOES IT REDUCE STUDENTS’ GRAMMATICAL ERRORS IN WRITING?”. Getsempena English Education Journal 6, no. 1 (May 31, 2019): 1–12. Accessed August 6, 2026. https://ejournal.bbg.ac.id/index.php/geej/article/view/858.