Wienhage, G. H., E. S. Ramos, L. M. Chiarello, V. Botton, and V. R. Wiggers. “Acidity Reduction of Bio-Oil by Methylic Esterification Reactions”. Angolan Mineral, Oil & Gas Journal, Vol. 2, no. 2, Apr. 2021, pp. 21-27, doi:10.47444/amogj.v2i2.4.