Unpikul, Boonkit, Thanawat Khanapang, Pawaris Pachsila, Worawut Auipako, and Primprapa Junlabuddee. “Design and Development of a Semi-Automatic Robusta Coffee Bean Sorting Machine with Optimal Operating Conditions Determined by Response Surface Methodology”. Thai Industrial Engineering Network Journal 12, no. 1 (June 30, 2026). accessed September 11, 2026. https://ph02.tci-thaijo.org/index.php/ienj/article/view/265032.