Periodic solutions of a certain generalized Liénard equation

We are concerned with the existence of at least one periodic solution of a generalized nonlinear Lienard equation with a periodic forcing term. The main tool is a continuation theorem by Capietto, Mawhin and Zanolin. A priori bounds for the periodic solutions are obtained either by studying the behavior of the trajectories of a new equivalent system or by determining the nature of singular points at infinity of suitable autonomous systems in the usual phase plane.