สิงห์คำน., ชมภูคำว., and ชมภูคำพ. “Development of Mathematics Activity Through Cooperative Learning With the Geometer’s Sketchpad Program to Encourage Learning Achievement and Creative Thinking Skills of Mathayomsuksa 2 Students”. Journal of Graduate Research, Vol. 9, no. 2, Dec. 2018, pp. 1-20, https://www.tci-thaijo.org/index.php/banditvijai/article/view/133933.