@article{CMH_1961__36_139240,
     author = {Kurt Strebel},
     title = {Zur {Frage} der {Eindeutigkeit} extremaler quasikonformer {Abbildungen} des {Einheitskreises.}},
     journal = {Commentarii mathematici Helvetici},
     pages = {306--323},
     year = {1961},
     volume = {36},
     zbl = {0112.05402},
     url = {http://geodesic.mathdoc.fr/item/CMH_1961__36_139240/}
}