W. Z. Wan Kamis, W. N. Azuwar, N. A. Ali Bashah, N. Isa, and S. S. A. Syed-Hassan, “Catalytic Esterification of Palm Fatty Acid Distillate to Produce Fatty Acid Methyl Ester ”, NTPSR-V4, pp. 91–98, May 2022.