Kuswara, R. Didi, et al. “Online Didactical Design for Subtraction Fractions: A Didactical Design Research through Lesson Study Activities”. International Journal of Didactic Mathematics in Distance Education, vol. 1, no. 1, Apr. 2024, pp. 37-46, http://jurnal.ut.ac.id/index.php/ijdmde/article/view/7772.