@article{CMH_1942__15_138810,
     author = {Alexandre Ostrowski},
     title = {Sur les conditions de validit\'e d'une classe de relations entre les expressions diff\'erentielles lin\'eaires.},
     journal = {Commentarii mathematici Helvetici},
     pages = {265--286},
     publisher = {mathdoc},
     volume = {15},
     year = {1942},
     zbl = {0027.39902},
     url = {http://geodesic.mathdoc.fr/item/CMH_1942__15_138810/}
}