Achmad Hilal Madjdi, Atik Rokhayani and Muh. Syafei. 2020. “Developing the Materials of Teaching English As a Foreign Language (TEFL) Subject through Lesson Study”. International Journal of Advanced Science and Technology 29 (08), 932 -39. http://sersc.org/journals/index.php/IJAST/article/view/19248.