Ismail, A. S., and Y. O. Aderinto. “On Characterization of Optimal Control Model of Whooping Cough”. Earthline Journal of Mathematical Sciences 8, no. 1 (December 20, 2021): 175-188. Accessed September 30, 2023. https://earthlinepublishers.com/index.php/ejms/article/view/439.