Udofia *, E.S., J.I. Uwakwe †, and H.S. Thomas. “Optimal Control and Sensitivity Analysis of Age-Structured Mathematical Model of Diphtheria Infection”. International Journal of Mathematical Analysis and Modelling 7, no. 1 (June 30, 2024). Accessed September 12, 2026. https://journal.tnsmb.org/index.php/ijmam/article/view/139.