Ngamjaroen, Sureerat, Watit Pakdee, and Cattaleeya Pattamaprom. 2015. “The Effect of Storage Degradation of Palm- Stearin Biodiesel on Engine Performance and Exhaust Emission”. Science & Technology Asia 15 (5):32-38. https://ph02.tci-thaijo.org/index.php/SciTechAsia/article/view/41237.