BOUA, H. Upper semi-Fredholm and Kato spectrum of an $\alpha$-times integrated semigroup. Methods of Functional Analysis and Topology, [S. l.], v. 26, n. 1, p. 63–67, 2020. DOI: https://doi.org/10.31392/MFAT-npu26_1.2020.04. Disponível em: https://zen.imath.kiev.ua/index.php/mfat/article/view/744. Acesso em: 13 dec. 2025.