APREUTESEI, Narcisia C.; VOLPERT, Vitaly A. Properness and topological degree for nonlocal integro-differential systems. Topological Methods in Nonlinear Analysis, [S. l.], v. 43, n. 1, p. 215–229, 2016. Disponível em: https://apcz.umk.pl/TMNA/article/view/TMNA.2014.012. Acesso em: 8 jul. 2025.