FELTRIN, G.; ZANOLIN, F. An application of coincidence degree theory to cyclic feedback type systems associated with nonlinear differential operators. Topological Methods in Nonlinear Analysis, [S. l.], v. 50, n. 2, p. 683–726, 2017. Disponível em: https://apcz.umk.pl/TMNA/article/view/TMNA.2017.038. Acesso em: 25 apr. 2024.