R. Ortega et A. Tineo, RESONANCE AND NONRESONANCE IN A PROBLEM OF BOUNDEDNESS, Proceedings of the American Mathematical Society, 124(7), 1996, pp. 2089-2096
This paper studies the existence of bounded solutions of a forced non-
linear differential equation of arbitrary order. Necessary and suffici
ent conditions for the existence of such solutions are obtained. These
results are inspired by classical results on the periodic problem, bo
th in the resonant and non-resonant cases.