Hassan O. B, Ojeyemi M. O. Efficacy of Polyphosphoric Acid in Reducing the Degree of Thermal Aging of Agbabu Natural Bitumen. CJPL [Internet]. 2017 Jan. 26 [cited 2024 May 6];4(2). Available from: https://journals.covenantuniversity.edu.ng/index.php/cjpls/article/view/405