Panyatanakun, Rachen, Sasiya Siriphanich, Uamporn Teeravuttichai, and Am-on Aungsuratana. 2001. “An Appropriate Agricultural Extension System for Central Region of Thailand”. Kasetsart Journal of Social Sciences 22 (2):155-64. https://so04.tci-thaijo.org/index.php/kjss/article/view/243464.