@article{CMH_1961__36_139225,
     author = {Jussi V\"ais\"al\"a and F.W. Gehring},
     title = {On the {Geometric} {Definition} for {Quasiconformal} {Mappings.}},
     journal = {Commentarii mathematici Helvetici},
     pages = {19--32},
     publisher = {mathdoc},
     volume = {36},
     year = {1961},
     zbl = {0104.29903},
     url = {http://geodesic.mathdoc.fr/item/CMH_1961__36_139225/}
}