Soopunyo, W., A. Ratana-Ubol, W. Pathumcharoenwattana, and S. Charungkaittikul. “Incorporating Non-Formal Learning and Education into Formal Schooling Conditions”. Journal of Education Studies, vol. 43, no. 3, Oct. 2015, pp. 39-49, https://so02.tci-thaijo.org/index.php/EDUCU/article/view/40544.