Imam, A., M. Balarabe, S. Kasim, and C. Eze. “Perfect Product of Two Squares in Finite Full Transformation Semigroup”. International Journal of Mathematical Sciences and Optimization: Theory and Applications, Vol. 11, no. 1, Apr. 2025, pp. 107-13, https://ijmso.unilag.edu.ng/article/view/2462.