Imam, A. T., L. Usman, A. Idris, and S. Ibrahim. “Product of Quasi-Idempotents in Finite Semigroup of Partial Order-Preserving Transformations.”. International Journal of Mathematical Sciences and Optimization: Theory and Applications 10, no. 1 (February 18, 2024): 53 - 59. Accessed November 25, 2024. http://ijmso.unilag.edu.ng/article/view/2046.