@article{JRAM_1934__170_149874,
     author = {Karl B\"ogel},
     title = {Mehrdimensionale {Differentiation} von {Funktionen} mehrerer reeller {Ver\"anderlichen.}},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {197--217},
     publisher = {mathdoc},
     volume = {170},
     year = {1934},
     zbl = {0008.25005},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1934__170_149874/}
}