@article{GDZPPN002337517, title = {Quasiregular mappings of the Heisenberg group.}, journal = {Mathematische Annalen}, volume = {293}, year = {1992}, pages = {625-644}, zbl = {0754.30018}, url = {http://dml.mathdoc.fr/item/GDZPPN002337517} }
Holopainen, Ilkka; Rickman, Seppo. Quasiregular mappings of the Heisenberg group.. Mathematische Annalen, Tome 293 (1992) pp. 625-644. http://gdmltest.u-ga.fr/item/GDZPPN002337517/