คล้ายมนต์ สุทิน. “dbFRec for DOS : A Database for Fertilizer Recommendaion Program”. Thai Agricultural Research Journal 15, no. 2 (March 23, 1997): 115–119. accessed September 30, 2026. https://li01.tci-thaijo.org/index.php/thaiagriculturalresearch/article/view/236557.