@article{Dmitrienko_Zvyagin_2003, title={Index of solution set for perturbed Fredholm equations and existence of periodic solutions for delay differential equations}, volume={21}, url={https://apcz.umk.pl/TMNA/article/view/TMNA.2003.004}, abstractNote={We consider the index of the solution set of Fredholm equations with $f$-condensing type perturbations. This characteristic is applied to the existence of periodic solutions for delay differential equations.}, number={1}, journal={Topological Methods in Nonlinear Analysis}, author={Dmitrienko, Vladimir T. and Zvyagin, Viktor G.}, year={2003}, month={Mar.}, pages={53–80} }