GRAFF, Grzegorz; NOWAK-PRZYGODZKI, Piotr. Fixed point indices of iterations of planar homeomorphisms. Topological Methods in Nonlinear Analysis, [S. l.], v. 22, n. 1, p. 159–166, 2003. Disponível em: https://apcz.umk.pl/TMNA/article/view/TMNA.2003.033. Acesso em: 1 jul. 2025.