@article{CMH_1942__15_138805,
     author = {Alexandre Ostrowski},
     title = {Sur un th\'eor\`eme fondamental de la th\'eorie des \'equations lin\'eaires aux d\'eriv\'ees partielles.},
     journal = {Commentarii mathematici Helvetici},
     pages = {217--221},
     publisher = {mathdoc},
     volume = {15},
     year = {1942},
     zbl = {0028.06201},
     url = {http://geodesic.mathdoc.fr/item/CMH_1942__15_138805/}
}