Butngam, O. . ., I. . . Srisombut, and D. . . Thotong. “The Study of Larning Outcomes and Problem Solving Skll Toward Grade Students Taught by Problem Based Learning”. Academic MCU Buriram Journal, vol. 2, no. 1, June 2017, pp. 74-82, https://so06.tci-thaijo.org/index.php/ambj/article/view/241617.