ŻOŁĄDEK, H. The classification of reversible cubic systems with center. Topological Methods in Nonlinear Analysis, [S. l.], v. 4, n. 1, p. 79–136, 1994. Disponível em: https://apcz.umk.pl/TMNA/article/view/TMNA.1994.024. Acesso em: 23 apr. 2024.