จิตต์โสภณ ค. and ธุวดาราตระกูล ส. 2020. Factors Affecting the Loyalty of the Farmers Growing Oil Palms towards Crude Palm Oil Extraction Plants in the Upper Southern Thailand . Journal of Graduate School, Pitchayatat, Ubon Ratchathani Rajabhat University. 15, 3 (Dec. 2020), 23–37.