HASSAN O., B.; OJEYEMI M., O. Efficacy of Polyphosphoric Acid in Reducing the Degree of Thermal Aging of Agbabu Natural Bitumen. Covenant Journal of Physical and Life Sciences, [S. l.], v. 4, n. 2, 2017. Disponível em: https://journals.covenantuniversity.edu.ng/index.php/cjpls/article/view/405. Acesso em: 6 may. 2024.