Hassan O., Bakare, and Olabemiwo Ojeyemi M. “Efficacy of Polyphosphoric Acid in Reducing the Degree of Thermal Aging of Agbabu Natural Bitumen”. Covenant Journal of Physical and Life Sciences 4, no. 2 (January 26, 2017). Accessed July 18, 2024. https://journals.covenantuniversity.edu.ng/index.php/cjpls/article/view/405.