Lyapunov Center Theorem of Infinite Dimensional Hamiltonian Systems. Analysis in Theory and Applications, [S. l.], v. 36, n. 3, p. 295–325, 2021. DOI: 10.4208/ata.OA-SU9. Disponível em: https://www.global-sci.com/index.php/ata/article/view/8200. Acesso em: 5 dec. 2025.