@article{JEDP_1988____A5_0,
     author = {Gourdin, Daniel},
     title = {Classes d'op\'erateurs faiblement hyperboliques non lin\'eaires},
     journal = {Journ\'ees \'equations aux d\'eriv\'ees partielles},
     eid = {5},
     pages = {1--16},
     publisher = {Ecole polytechnique},
     year = {1988},
     zbl = {0679.35008},
     language = {fr},
     url = {http://www.numdam.org/item/JEDP_1988____A5_0/}
}