@article{MAN_1940__117_160068,
     author = {G. Tautz},
     title = {Zur {Theorie} der elliptischen {Differentialgleichungen.} {I.}},
     journal = {Mathematische Annalen},
     pages = {694--726},
     publisher = {mathdoc},
     volume = {117},
     year = {1940},
     zbl = {67.0353.02},
     url = {http://geodesic.mathdoc.fr/item/MAN_1940__117_160068/}
}