M.I. Umar, M.U. Adehi, and M.A. Auwal. “A Systematic Review of Multi-Server Queueing System: A Case of Lengthy Wait Times in Hospital Medical Outpatient Department (OPD)”. African Journal of Advances in Science and Technology Research 12, no. 1 (October 3, 2023): 01–17. Accessed November 2, 2026. https://publications.afropolitanjournals.com/index.php/ajastr/article/view/601.