H. Majeed, Abdulrahman, and Mushreq I. Meften. “Centralizers of Prime and Semiprime Rings”. Journal of Al-Qadisiyah for Computer Science and Mathematics, vol. 1, no. 1, Aug. 2017, pp. 58-66, https://jqcsm.qu.edu.iq/index.php/journalcm/article/view/167.