@article{MZ_1929__29_168091,
     author = {J. Popken},
     title = {Zur {Transzendenz} von e.},
     journal = {Mathematische Zeitschrift},
     pages = {525--541},
     publisher = {mathdoc},
     volume = {29},
     year = {1929},
     language = {de},
     url = {http://geodesic.mathdoc.fr/item/MZ_1929__29_168091/}
}