@article{MAN_1940__117_160067,
     author = {O. Perron},
     title = {Das {Verschwinden} der {Klammersymbole} in der {Theorie} der linearen partiellen {Differentialgleichungssysteme} .},
     journal = {Mathematische Annalen},
     pages = {687--693},
     publisher = {mathdoc},
     volume = {117},
     year = {1940},
     zbl = {67.0331.01},
     url = {http://geodesic.mathdoc.fr/item/MAN_1940__117_160067/}
}