New oscillation criteria for a class of second-order nonlinear forced differential equations

By using classical variational principle and averaging technique, new oscillation criteria are established for second-order nonlinear forced differential equations r(t)ψ x(t) φ x (t) + q(t)f x(t) = e(t), t t0, where the functions r, q, e ∈ C([t0,∞),R), and φ,ψ,f ∈ C(R,R) improve and extend some recent results. © 2007 Elsevier Inc. All rights reserved.