@article{EJDE_2013__2013__a94,
     author = {Gu, Hua and An, Tianqing},
     title = {Existence of infinitely many periodic solutions for second-order {Hamiltonian} systems},
     journal = {Electronic Journal of Differential Equations},
     publisher = {mathdoc},
     volume = {2013},
     year = {2013},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/EJDE_2013__2013__a94/}
}