中国科学院数学与系统科学研究院期刊网
AMS
Multiplicity of Periodic Solutions for Second Order Hamiltonian Systems with Asymptotically Quadratic Conditions
Peng LIU, Fei GUO
Acta Mathematica Sinica . 2020, (1): 55 -65 .  DOI: 10.1007/s10114-019-9141-7