@article{RLIN_1995_9_6_3_a2,
     author = {Giannoni, Fabio and Masiello, Antonio},
     title = {On a variational theory of light rays on {Lorentzian} manifolds},
     journal = {Atti della Accademia nazionale dei Lincei. Rendiconti Lincei. Matematica e applicazioni},
     pages = {155--159},
     publisher = {mathdoc},
     volume = {Ser. 9, 6},
     number = {3},
     year = {1995},
     zbl = {0848.53041},
     mrnumber = {619853},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/RLIN_1995_9_6_3_a2/}
}