Khowjoy, Kritchai. 2022. “Relationship between Key Factors of Operation Management Affecting the Operation Cost in Phetchabun Small and Medium Industrial Entrepreneurs: Variables in Manufacture Defect and Operating Times”. Ratchaphruek Journal 20 (1):14-26. https://so05.tci-thaijo.org/index.php/Ratchaphruekjournal/article/view/253654.