Periodic solutions of convex neutral functional differential equations

Abstract

In this paper we consider the existence of periodic solutions of neutral functional differential equations. It has been proved that for convex neutral functional differential equations of $D$-operator type with finite (or infinite) delay and hyperneutral functional differential equations with finite delay, there is a periodic solution if and only if there is a bounded solution. The results proved by Massera, Chow and Makay are generalized.