Leong Boon Soon, Anika Zafiah M. Rus, Sulaiman Hasan, “Continuous Biodiesel Production using Ultrasound Clamp on Tubular Reactor”, Int. J. Automot. Mech. Eng., vol. 8, pp. 1396–1405, Dec. 2022, doi: 10.15282/ijame.8.2013.27.0115.