Gowri Krishnan, Shamala, Fei-ling Pua, Kumaran Palanisamy, Sharifah Nabihah Syed Jaafar, and Koguleshun Subramaniam. “Oil Palm Empty Fruit Bunches Fiber-Supported Heterogeneous Acid Catalyst for Esterification of Oleic Acid: Effect of Different Transition Metal Sulfate”. International Journal of Engineering & Technology 7, no. 4.35 (November 30, 2018): 870–875. Accessed April 29, 2024. https://www.sciencepubco.com/index.php/ijet/article/view/26272.