PATSYUCK, O. M. On stable $\mathcal{C}$-symmetries for a class of $\mathcal{PT}$-symmetric operators. Methods of Functional Analysis and Topology, [S. l.], v. 19, n. 1, p. 73–79, 2013. Disponível em: https://zen.imath.kiev.ua/index.php/mfat/article/view/537. Acesso em: 16 dec. 2025.