@article{IM_1985__80_143233,
     author = {H.M. Reimann and A. Kor\'anyi},
     title = {Quasiconformal mappings on the {Heisenberg} group.},
     journal = {Inventiones mathematicae},
     pages = {309--338},
     year = {1985},
     volume = {80},
     zbl = {0567.30017},
     url = {http://geodesic.mathdoc.fr/item/IM_1985__80_143233/}
}