Singto, A. “THE DEVELOPMENT OF STEM EDUCATION LEARNING ACTIVITIES TO ENHANCE PROBLEM SOLVING THINKING ABILITY FOR MATHAYOMSUKSA 1”. Journal of MCU Nakhondhat, vol. 7, no. 7, July 2020, pp. 387-98, https://so03.tci-thaijo.org/index.php/JMND/article/view/245023.