Suksringarm, J., Singseewo, A., and Appamaraka, S. “Development of knowledge, awareness, critical thinking and argumentation of the 9th grade’s students taught socio-environmental issues using mixed methods based on adapted problem-based learning”. International Journal of Agricultural Technology, vol. 15, no. 3, May 2019, pp. 501-18, https://li04.tci-thaijo.org/index.php/IJAT/article/view/8234.