Songchai, R., and J. Ardkaew. “A Comparisons of Learning Achievements and Analytical Thinking Abilities in Mathematics of Prathomsuksa 5 Students Between Using The Problem Based Learning (PBL) and The Traditional Teaching Model”. Trends of Humanities and Social Sciences Research, vol. 7, no. 2, Aug. 2019, pp. 24-41, https://so03.tci-thaijo.org/index.php/Humanties-up/article/view/209798.