@article{CMH_1981__56_139884,
     author = {Richard Fehlmann},
     title = {Ueber extremale quasikonforme {Abbildungen.}},
     journal = {Commentarii mathematici Helvetici},
     pages = {558--580},
     publisher = {mathdoc},
     volume = {56},
     year = {1981},
     zbl = {0504.30008},
     url = {http://geodesic.mathdoc.fr/item/CMH_1981__56_139884/}
}