Setiyani, D. P. Putri, F. Ferdianto, and S. H. Fauji. “Designing a Digital Teaching Module Based on Mathematical Communication in Relation and Function”. Journal on Mathematics Education, vol. 11, no. 2, May 2020, pp. 223-36, http://jme.ejournal.unsri.ac.id/index.php/jme/article/view/3668.