@incollection{JEDP_1978____A11_0,
     author = {Gourdin, Daniel},
     title = {Syst\`emes hyperboliques \`a caract\'eristiques de multiplicit\'e variable},
     booktitle = {},
     series = {Journ\'ees \'equations aux d\'eriv\'ees partielles},
     eid = {11},
     pages = {1--2},
     publisher = {Ecole polytechnique},
     year = {1978},
     mrnumber = {58 #23112},
     language = {fr},
     url = {http://archive.numdam.org/item/JEDP_1978____A11_0/}
}