Gabor, Dorota. “Remarks to the Orientation and Homotopy in Coincidence Problems Involving Fredholm Operators of Nonnegative Index”. Topological Methods in Nonlinear Analysis 31, no. 1 (March 1, 2008): 161–190. Accessed July 22, 2024. https://apcz.umk.pl/TMNA/article/view/TMNA.2008.009.