Pitaloka, D.A. et al. 2025. Trenggalek Durian Peel Ash a K2O Catalyst in Ultrasonic Biodiesel Production. Journal of The Indonesian Society of Integrated Chemistry. 17, 2 (Dec. 2025), 83–91. DOI:https://doi.org/10.22437/jisic.v17i2.49504.