@article{MZ_1929__29_168058,
     author = {W. Ephr\"amowitsch},
     title = {Zur {Theorie} der nicht orientierbaren {Mannigfaltigkeiten}},
     journal = {Mathematische Zeitschrift},
     pages = {55--59},
     publisher = {mathdoc},
     volume = {29},
     year = {1929},
     language = {de},
     url = {http://geodesic.mathdoc.fr/item/MZ_1929__29_168058/}
}