@article{CMH_1968__43_139359,
     author = {H. Renggli},
     title = {Doppelverh\"altnisse und quasikonforme {Abbildungen.}},
     journal = {Commentarii mathematici Helvetici},
     pages = {161--175},
     year = {1968},
     volume = {43},
     zbl = {0159.10902},
     url = {http://geodesic.mathdoc.fr/item/CMH_1968__43_139359/}
}