F. Ahmadi, S. E. Mulyono, B. A. A.-R. Al-Ghamdi, and D. Harjunowibowo, “Comparative Study of the Development of Android-Based Flipped Classroom Model between Jeddah and Indonesia”, Int. J. Adv. Sci. Eng. Inf. Technol., vol. 10, no. 2, pp. 542–547, Apr. 2020.