@article{JRAM_1929__161_149691,
     author = {Harald Geppert},
     title = {Zur {Theorie} des {Borchardtschen} {Mittels.} {I.}},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {21--40},
     publisher = {mathdoc},
     volume = {161},
     year = {1929},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1929__161_149691/}
}