Periodic solutions for a class of nonautonomous second order Hamiltonian systems ✩

In this paper, some existence theorems of periodic solutions of a class of the nonautonomous second order Hamiltonian systems ¨ x(t) − B(t)x(t)+∇H t,x(t) = 0, ∀t ∈ [0,T ], are obtained by a mountain pass theorem and a local link theorem. © 2007 Elsevier Inc. All rights reserved