Väth, Martin. “An Axiomatic Approach to a Coincidence Index for Noncompact Function Pairs”. Topological Methods in Nonlinear Analysis 16, no. 2 (December 1, 2000): 307–338. Accessed July 22, 2024. https://apcz.umk.pl/TMNA/article/view/TMNA.2000.043.