Boundedness of solutions for second order differential equations with asymmetric nonlinearity

In this paper we are concerned with the boundedness of all solutions of the second order differential equations ¨x +f (˙x)+ ax+ −bx− +g(x) = p(t), where (a, b) does not lie on one of the Fuˇcik spectrum curves, the functions f and g are bounded, and p is 2π-periodic.  2005 Elsevier Inc. All rights reserved.