E. C. . H. Cadiao Philippines and M. J. . B. Tan, “Effectiveness of Using a Flipped Classroom in Improving English Grammar Proficiency”, IJSBAR, vol. 51, no. 2, pp. 45–57, Apr. 2020, Accessed: Sep. 12, 2025. [Online]. Available: https://www.gssrr.org/JournalOfBasicAndApplied/article/view/10943