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)r,q,e∈C([t0,∞),R), and ϕ,ψ,f∈C(R,R)ϕ,ψ,f∈C(R,R) improve and extend some recent results.