@article{JMPA_1920_8_3__65_0,
     author = {Janet, Maurice},
     title = {Sur les syst\`emes d'\'equations aux d\'eriv\'ees partielles},
     journal = {Journal de Math\'ematiques Pures et Appliqu\'ees},
     pages = {65--151},
     publisher = {Gauthier-Villars},
     volume = {8e s{\'e}rie, 3},
     year = {1920},
     language = {fr},
     url = {http://www.numdam.org/item/JMPA_1920_8_3__65_0/}
}