@article{CMH_1952__26_139044,
     author = {Hans Wittich},
     title = {Bemerkung zum {Typenproblem.}},
     journal = {Commentarii mathematici Helvetici},
     pages = {180--183},
     publisher = {mathdoc},
     volume = {26},
     year = {1952},
     zbl = {0049.06303},
     url = {http://geodesic.mathdoc.fr/item/CMH_1952__26_139044/}
}