Baikulab, K. ., S. . Juithong, and K. Kanreutai. “The Effects of Problem-Based Learning Activities in Mathematics towards Equation Problem Solving Ability of Grade 6 Students”. Muban Chombueng Rajabhat University Research Journal (Humanities and Social Science), vol. 7, no. 1, June 2020, pp. 140-52, https://so03.tci-thaijo.org/index.php/hssj/article/view/248502.