ยุ่นแก้ว ศ., and ชมภู ส. “Efficient Implementation of 15-Year Free Education Scheme in the Schools of the Secondary Educational Service Area Office 40”. Rajapark Journal, vol. 11, no. 21, Feb. 2017, pp. 179-85, https://so05.tci-thaijo.org/index.php/RJPJ/article/view/171732.