Chamorro Portilla, Erika Gysell, et al. “Obtaining Biodiesel from Used Oil”. Boletí­n Informativo CEI, vol. 5, no. 2, Aug. 2018, pp. 86-92, https://revistas.umariana.edu.co/index.php/BoletinInformativoCEI/article/view/1661.