Periodic solutions to non-autonomous second-order systems Original Research Article

We establish the existence of periodic solution of a class of non-autonomous second-order systems, View the MathML sourceẍ+μx+V(t,x)=0, where V(t,x)=(v1(t,x),…,vn(t,x))V(t,x)=(v1(t,x),…,vn(t,x)), if View the MathML sourcelim|x|→∞vi(t,x)|x|=0,i=1,…,n, uniformly in tt and VV is bounded below or above for appropriate ranges of μμ.