@article{MZ_1951__54_169215,
     author = {Hans L\"obell},
     title = {Der },
     journal = {Mathematische Zeitschrift},
     pages = {129--135},
     year = {1951},
     volume = {54},
     zbl = {0043.36305},
     url = {http://geodesic.mathdoc.fr/item/MZ_1951__54_169215/}
}