@article{MAN_1910__69_158476,
     author = {M. Hafen},
     title = {Studien \"uber einige {Probleme} der {Potentialtheorie.} {(Mit} 3 {Figuren} im {Text)}},
     journal = {Mathematische Annalen},
     pages = {517--537},
     publisher = {mathdoc},
     volume = {69},
     year = {1910},
     zbl = {41.0857.01},
     url = {http://geodesic.mathdoc.fr/item/MAN_1910__69_158476/}
}