@article{MZ_1942__47_168930,
     author = {H., Schubert},
     title = {Ein potentialtheoretischer {Hilfssatz}},
     journal = {Mathematische Zeitschrift},
     pages = {8--15},
     year = {1942},
     volume = {47},
     zbl = {66.0449.02},
     url = {http://geodesic.mathdoc.fr/item/MZ_1942__47_168930/}
}