@article{AIHPA_1998__69_4_359_0,
     author = {Giannoni, F. and Masiello, A. and Piccione, P.},
     title = {A {Morse} theory for light rays on stably causal lorentzian manifolds},
     journal = {Annales de l'I.H.P. Physique th\'eorique},
     pages = {359--412},
     publisher = {Gauthier-Villars},
     volume = {69},
     number = {4},
     year = {1998},
     mrnumber = {1659591},
     zbl = {0920.58019},
     language = {en},
     url = {http://www.numdam.org/item/AIHPA_1998__69_4_359_0/}
}