Y. M. Karimah, S. Dampang, A. S. Nazhifa, R. Alfiyah, and A. Jayanti, “Effects of Reaction Temperature and Phosphoric Acid Catalyst Volume on Free Fatty Acid Reduction in Used Cooking Oil via Esterification”, SAINTEKS, vol. 8, no. 02, pp. 313–323, Sep. 2026.