Chotikhamjorn, Supitcha. “Study of Production Efficiency and Maize Farmers’ Incomes in Phetchabun Province”. Humanities and Social Sciences Journal of Pibulsongkram Rajabhat University 15, no. 2 (June 17, 2021): 317–330. Accessed May 6, 2024. https://so01.tci-thaijo.org/index.php/GraduatePSRU/article/view/239835.