VÄTH, M. A general degree for function triples. Topological Methods in Nonlinear Analysis, [S. l.], v. 41, n. 1, p. 163–190, 2013. Disponível em: https://apcz.umk.pl/TMNA/article/view/TMNA.2013.007. Acesso em: 4 may. 2024.