YEN, C.-T. ON RINGS SATISFYING BOTH OF 1-abc AND 1-cba BEING INVERTIBLE OR NONE. Tamkang Journal of Mathematics, [S. l.], v. 24, n. 3, p. 317–321, 1993. DOI: 10.5556/j.tkjm.24.1993.4503. Disponível em: https://journals.math.tku.edu.tw/index.php/TKJM/article/view/4503. Acesso em: 5 jul. 2022.