@article{EJDE_2005__2005__a215,
     author = {Bonanno,  Gabriele and Livrea,  Roberto},
     title = {Periodic solutions for a class of second-order {Hamiltonian} systems},
     journal = {Electronic journal of differential equations},
     year = {2005},
     volume = {2005},
     zbl = {1096.34027},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/EJDE_2005__2005__a215/}
}