H. Shuker, Nazar, Husam Q. Mohammad, and Shaimaa H. Ahmad. “On Singular and Non Singular Rings”. AL-Rafidain Journal of Computer Sciences and Mathematics 3, no. 1 (June 3, 2006): 111–116. Accessed December 18, 2025. https://csmj.uomosul.edu.iq/index.php/csmj/article/view/37084.