Abdullah, Abdul Halim, and Bomi Shin. “A Comparative Study of Quadrilaterals Topic Content in Mathematics Textbooks Between Malaysia and South Korea”. Journal on Mathematics Education 10, no. 3 (September 3, 2019): 315–340. Accessed July 29, 2025. https://jme.ejournal.unsri.ac.id/index.php/jme/article/view/3797.