RASHID, M. H. M. Extended Weyl theorems and perturbations. Methods of Functional Analysis and Topology, [S. l.], v. 19, n. 1, p. 80–96, 2013. Disponível em: https://zen.imath.kiev.ua/index.php/mfat/article/view/538. Acesso em: 16 dec. 2025.