FRING, A. PT-symmetry and Integrability. Acta Polytechnica, [S. l.], v. 47, n. 2-3, 2007. DOI: 10.14311/934. Disponível em: https://ojst.is.cvut.cz/ojs/index.php/ap/article/view/934.. Acesso em: 12 may. 2025.