@article{RSMUP_1994__91__251_0,
     author = {Greco, Carlo},
     title = {Infinitely many spacelike periodic trajectories on a class of {Lorentz} manifolds},
     journal = {Rendiconti del Seminario Matematico della Universit\`a di Padova},
     pages = {251--263},
     publisher = {Seminario Matematico of the University of Padua},
     volume = {91},
     year = {1994},
     mrnumber = {1289640},
     zbl = {0807.53055},
     language = {en},
     url = {http://www.numdam.org/item/RSMUP_1994__91__251_0/}
}