ชมภู บ. “Comparisons of Learning Achievements, Analytical Thinking Abilities, Satisfaction with Learning and Teaching, and Learning Retention in the Mathematics Learning Strand Entitled Trigonometrical Ratios of Matthayomsueksa 4 Students Using Courseware Geometer’s Sketchpad Approach (CGS) and the Conventional Teaching Approach”. Academic Journal of Thailand National Sports University, vol. 2, no. 1, May 2010, pp. 155-6, https://he02.tci-thaijo.org/index.php/TNSUJournal/article/view/252168.