VÄTH, M. Degree and index theories for noncompact function triples. Topological Methods in Nonlinear Analysis, [S. l.], v. 29, n. 1, p. 79–117, 2007. Disponível em: https://apcz.umk.pl/TMNA/article/view/TMNA.2007.005. Acesso em: 28 mar. 2024.