Small periodic solutions of nonlinear systems of differential equations with constant deviation (Q954162)

The paper is devoted to the study of the existence of small periodic solutions to a nonlinear system of differential equations with a singular matrix at the derivatives, with a vector deviation depending on a parameter. Using some methods of the fixed point theory for nonlinear operators and other methods, the author reduces the above-mentioned problem to the question of the solvability of an operator equation, whose principal part is defined in a finite-dimensional space.