@article{AIHPA_1972__17_2_131_0,
     author = {Pommaret, J. F.},
     title = {\'Etude interne des syst\`emes lin\'eaires d'\'equations aux d\'eriv\'ees partielles},
     journal = {Annales de l'institut Henri Poincar\'e. Section A, Physique Th\'eorique},
     pages = {131--158},
     publisher = {Gauthier-Villars},
     volume = {17},
     number = {2},
     year = {1972},
     mrnumber = {348802},
     zbl = {0253.35015},
     language = {fr},
     url = {http://www.numdam.org/item/AIHPA_1972__17_2_131_0/}
}