The purpose of this paper is to study the multiplicity of periodic solutions for a class of non-autonomous second-order damped vibration systems. New results are obtained by using Fountain theorem. These results improve the related ones in the literature.

中文翻译：

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二阶阻尼振动系统周期解的新结果

本文的目的是研究一类非自治二阶阻尼振动系统的周期解的多重性。通过使用Fountain定理可以获得新的结果。这些结果改进了文献中的相关结果。