A multiplicity theorem for critical points offunctionals on reflexive Banach spaces

In this paper we establish a multiplicity theorem for critical points offunctionals on reflexive Banach spaces. Precisely, we deduce the main resultusing a general variational principle proved by Ricceri. Moreover,we present an application to a Neumann problem which gives apositive answer to some questions formulated by the previousauthor.Received: 6 February 2003