@article{CMH_1939__12_138749,
     author = {Arnold Emch},
     title = {Zwei {Abbildungs-Probleme.}},
     journal = {Commentarii mathematici Helvetici},
     pages = {246--253},
     year = {1939},
     volume = {12},
     url = {http://geodesic.mathdoc.fr/item/CMH_1939__12_138749/}
}