BHATTACHARYYA, J.; BASNET, D. K. . Formal triangular matrix ring with nil clean index 4. Journal of the Assam Academy of Mathematics, [S. l.], v. 13, p. 1–4, 2023. Disponível em: https://jaam.aamonline.org.in/ojs/index.php/j/article/view/60. Acesso em: 18 may. 2024.