เข็มโคกกรวด อ., and อนุตระกูลชัย ร. “A Study of Mathematical Skills and Decimal Division Achievement of Grade 6 Students Using the Constructivist Learning Theory and the Polya Problem-Solving Process”. Journal of MCU Nakhondhat, vol. 5, no. 2, Aug. 2018, pp. 136-51, https://so03.tci-thaijo.org/index.php/JMND/article/view/139484.