Garridos, Cristina, and Emily Amor Balase. “Students’ Level of Understanding of the Basic Concept of Functions and Relations: A Conceptual Analysis”. The Mindanawan Journal of Mathematics 2, no. 1 (October 1, 2011): 54–65. Accessed September 17, 2024. https://journals.msuiit.edu.ph/tmjm/article/view/19.