WuCZ07'

@article{DBLP:journals/mcm/WuCZ07,
  author    = {Xian Wu and
               Shao-Xiong Chen and
               Fukun Zhao},
  title     = {New existence and multiplicity theorems of periodic solutions
               for non-autonomous second order Hamiltonian systems},
  journal   = {Mathematical and Computer Modelling},
  volume    = {46},
  number    = {3-4},
  year      = {2007},
  pages     = {550-556},
  ee        = {http://dx.doi.org/10.1016/j.mcm.2006.11.019},
  bibsource = {DBLP, http://dblp.uni-trier.de}
}