@article{GDZPPN00206443X, title = {Ueber extremale quasikonforme Abbildungen.}, journal = {Commentarii mathematici Helvetici}, volume = {56}, year = {1981}, pages = {558-580}, zbl = {0504.30008}, url = {http://dml.mathdoc.fr/item/GDZPPN00206443X} }
Fehlmann, Richard. Ueber extremale quasikonforme Abbildungen.. Commentarii mathematici Helvetici, Tome 56 (1981) pp. 558-580. http://gdmltest.u-ga.fr/item/GDZPPN00206443X/