FITZPATRICK, P. M.; PEJSACHOWICZ, J.; RABIER, P. J. The degree of proper $C^2$ Fredholm mappings: Convariant theory. Topological Methods in Nonlinear Analysis, [S. l.], v. 3, n. 2, p. 325–367, 1994. Disponível em: https://apcz.umk.pl/TMNA/article/view/TMNA.1994.017. Acesso em: 22 lip. 2024.