Agarwal, Ravi P., Donal O’Regan, and Radu Precup. 2003. “Fixed Point Theory and Generalized Leray-Schauder Alternatives for Approximable Maps in Topological Vector Spaces”. Topological Methods in Nonlinear Analysis 22 (1):193-202. https://apcz.umk.pl/TMNA/article/view/TMNA.2003.036.