@article{MAN_1882__20_157049,
     author = {K\"onigsberger},
     title = {Ueber eine {Eigenschaft} der partiellen {Differentialgleichungen}},
     journal = {Mathematische Annalen},
     pages = {587--593},
     publisher = {mathdoc},
     volume = {20},
     year = {1882},
     zbl = {14.0289.02},
     url = {http://geodesic.mathdoc.fr/item/MAN_1882__20_157049/}
}