LLIBRE, J.; SALHI, T. The limit cycles of a class of quintic polynomial vector fields. Topological Methods in Nonlinear Analysis, [S. l.], v. 54, n. 1, p. 141–151, 2019. Disponível em: https://apcz.umk.pl/TMNA/article/view/TMNA.2019.030. Acesso em: 22 jul. 2024.