Gowri Krishnan, S. et al. 2018. 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, 4.35 (Nov. 2018), 870–875. DOI:https://doi.org/10.14419/ijet.v7i4.35.26272.