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://gsp.tricubic.dev/ata/article/view/8200. Acesso em: 16 mar. 2026.