The results of Berger and Chen are extended. And the variational method is proved to be available to solve the existence and uniqueness of the almost periodic solutions of nonlinear Duffing equations with damping.

• 推广了Berger和Chen的结果,证明了经典的变分方法对于解决带阻尼的非线性Duffing方程有界解的存在唯一性问题是同样适用的。