ASHRAF, M. SOME COMMUTATIVITY THEOREMS FOR ASSOCIATIVE RINGS WITH CONSTRAINTS INVOLVING A NIL SUDSET. Tamkang Journal of Mathematics, [S. l.], v. 22, n. 3, p. 285–297, 1991. DOI: 10.5556/j.tkjm.22.1991.4613. Disponível em: https://journals.math.tku.edu.tw/index.php/TKJM/article/view/4613. Acesso em: 18 aug. 2022.