Adaji, Mathew O., Stephen E. Onah, Richard A. Kimbir, and Terhemen Terhemen Aboiyar. 2018. “Financial Evaluation of Early Retirement Benefit in A Defined Benefit Plan”. International Journal of Mathematical Sciences and Optimization: Theory and Applications 2016 (April), 67 - 82. http://ijmso.unilag.edu.ng/article/view/20.