The paper is devoted to integro-differential operators, which correspond to nonlocal reaction-diffusion equations considered on the whole axis. Their Fredholm property and properness will be proved. This will allow one to define the topological degree.
N. Apreutesei. V. Volpert. "Properness and Topological Degree for Nonlocal Reaction-Diffusion Operators." Abstr. Appl. Anal. 2011 1 - 21, 2011. https://doi.org/10.1155/2011/629692