@article{CMUC_1987__28_4_a8,
     author = {Greco, Carlo},
     title = {Remarks on periodic solutions, with prescribed energy, for singular {Hamiltonian} systems},
     journal = {Commentationes Mathematicae Universitatis Carolinae},
     pages = {661--672},
     publisher = {mathdoc},
     volume = {28},
     number = {4},
     year = {1987},
     mrnumber = {928681},
     zbl = {0678.34052},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/CMUC_1987__28_4_a8/}
}