ZHENG, N.; WANG, Z. Infinitely many periodic solutions of Duffing equations under integral condition. Topological Methods in Nonlinear Analysis, [S. l.], v. 57, n. 1, p. 297–315, 2020. Disponível em: https://apcz.umk.pl/TMNA/article/view/TMNA.2020.017. Acesso em: 22 jul. 2024.