where ω > 0, : C([0,ω]) → L([0,ω]) is a linear bounded operator and q ∈ L([0,ω]). By a solution of the problem (1.1), (1.2) we understand a function u ∈ C̃′([0,ω]), which satisfies (1.1) almost everywhere on [0,ω] and satisfies the conditions (1.2). The periodic boundary value problem for functional differential equations has been studied by many authors (see, for instance, [1, 2, 3, 4, 5, 6, 8,...

In this paper we study the convergence of an iterative algorithm for finding zeros with constraints for not necessarily monotone set-valued operators in a reflexive Banach space. This algorithm, which we call the proximalprojection method is, essentially, a fixed point procedure and our convergence results are based on new generalizations of Lemma Opial. We show how the proximal-projection meth...