A nonlinear periodic averaging principle

This paper is devoted to a nonlinear averaging principle for periodic solutions of a class of second order inclusions. In addition an existence theorem for periodic solutions of such inclusions is established. This work which complements the abstract nonlinear averaging principle worked out in Couchouron and Kamenski (Nonlin. Anal. 42 (2000) 1101) makes a synthesis of the methods contained in Couchouron and Kamenski and Couchouron and Precup (Electron. J. Differential, Equations 4 (2002) 1) and represents a (nonvariational) topological approach for boundary values problems. [Copyright &y& Elsevier]