Shahrulzaman, Maimunah, and Hasnida Harun. “Performance of Magnetic Palm Oil Empty Fruit Bunch Biochar for Removal of Waste Cooking Oil”. Progress in Engineering Application and Technology, vol. 2, no. 2, Dec. 2021, pp. 065–074, https://penerbit.uthm.edu.my/periodicals/index.php/peat/article/view/870.