@article{MZ_1926__25_167893,
     author = {K. B\"ogel},
     title = {\"Uber partiell differenzierbare {Funktionen}},
     journal = {Mathematische Zeitschrift},
     pages = {490--498},
     year = {1926},
     volume = {25},
     zbl = {52.0241.06},
     url = {http://geodesic.mathdoc.fr/item/MZ_1926__25_167893/}
}