Abu Bakar, K., S. Mohamed, F. Yunus, and A. A. Karim. “Use of Multiple Representations in Understanding Addition: The Case of Pre-School Children”. International Journal of Learning, Teaching and Educational Research, vol. 19, no. 2, Feb. 2020, pp. 292-04, https://ijlter.myres.net/index.php/ijlter/article/view/476.