BALANOV, Z.; KRAWCEWICZ, W.; STEINLEIN, H. $SO(3)\times S^1$-equivariant degree with applications to symmetric bifurcation problems: the case of one free parameter. Topological Methods in Nonlinear Analysis, [S. l.], v. 20, n. 2, p. 335–374, 2002. Disponível em: https://apcz.umk.pl/TMNA/article/view/TMNA.2002.040. Acesso em: 3 jul. 2024.