Santia, Ika, Purwanto, Akbar Sutawidjadja, Sudirman, and Subanji. 2019. “Exploring Mathematical Representations in Solving Ill-Structured Problems: The Case of Quadratic Function”. Journal on Mathematics Education 10 (3):365-78. https://jme.ejournal.unsri.ac.id/index.php/jme/article/view/3800.