Sochaiyan, C., Phattarachaleeku ม., and N. Chutiman. “Development of Mathematical Problem Solving Skills Using Problem-Based Learning with Digital Media on Ratio, Proportion and Percentage for Mathayomsuksa 1 Students”. Journal of Education Rajabhat Maha Sarakham University, vol. 19, no. 3, Dec. 2022, pp. 201-14, https://so06.tci-thaijo.org/index.php/edu-rmu/article/view/261148.