@article{AIHPC_1999__16_6_725_0,
     author = {Liu, Chun-Gen and Long, Yiming},
     title = {Hyperbolic characteristics on star-shaped hypersurfaces},
     journal = {Annales de l'I.H.P. Analyse non lin\'eaire},
     pages = {725--746},
     publisher = {Gauthier-Villars},
     volume = {16},
     number = {6},
     year = {1999},
     mrnumber = {1720514},
     zbl = {0988.37078},
     language = {en},
     url = {http://archive.numdam.org/item/AIHPC_1999__16_6_725_0/}
}