A. Hammodat, Alaa, علاء, Ali A. Bilal, علی, Akram S. Mohammed, and اکرم. “Some Basic Properties of Idempotent Matrices”. Journal of Education and Science (JES) 21, no. 4 (December 1, 2008): 124–130. Accessed August 4, 2025. https://rjps.uomosul.edu.iq/index.php/edusj/article/view/18248.