BERGER, M. S.; ZHANG, L. New method for large quasiperiodic nonlinear oscillations with fixed frequencies for the nondissipative second type Duffing equation. Topological Methods in Nonlinear Analysis, [S. l.], v. 6, n. 2, p. 283–293, 1995. Disponível em: https://apcz.umk.pl/TMNA/article/view/TMNA.1995.046. Acesso em: 22 jul. 2024.