LLIBRE, J.; DA SILVA, M. F. Global phase portraits of Kukles differential systems with homogenous polynomial nonlinearities of degree 5 having a center. Topological Methods in Nonlinear Analysis, [S. l.], v. 48, n. 1, p. 257–282, 2016. Disponível em: https://apcz.umk.pl/TMNA/article/view/TMNA.2016.049. Acesso em: 22 jul. 2024.