von Haeseler, F., H.-O. Peitgen, and G. Skordev. “Lefschetz Fixed Point Theorem for Acyclic Maps With Multiplicity”. Topological Methods in Nonlinear Analysis, vol. 19, no. 2, June 2002, pp. 339-74, https://apcz.umk.pl/TMNA/article/view/TMNA.2002.018.