Mohamad Ketar@Mokhtar, Nur Izzah, and Hasnida Harun. “Synthesis of Magnetic Biochar Derived from Oil Palm Frond for Waste Cooking Oil Treatment”. Progress in Engineering Application and Technology, vol. 2, no. 2, Dec. 2021, pp. 116-2, https://penerbit.uthm.edu.my/periodicals/index.php/peat/article/view/944.