I. N. Pramesti, M. A. Iqbal, R. Retnosari, and L. Octaviana, “Ultrasonic-Assisted Synthesis of Methyl Ester Sulfonate (MES) from Coconut Oil via Transesterification and Sulfonation Using Eggshell-Derived CaO Catalyst ”, Al-Kimia, vol. 14, no. 1, Jun. 2026.