@article{JEDP_1988____A4_0,
     author = {Bernardi, Enrico and Bove, Antonio},
     title = {Conditions de {Levi} pour le probl\`eme de {Cauchy} pour une classe d'\'equations hyperboliques \`a caract\'eristique triples},
     journal = {Journ\'ees \'equations aux d\'eriv\'ees partielles},
     eid = {4},
     pages = {1--7},
     publisher = {Ecole polytechnique},
     year = {1988},
     mrnumber = {90b:35144b},
     zbl = {0676.35053},
     language = {fr},
     url = {http://archive.numdam.org/item/JEDP_1988____A4_0/}
}