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@article{CMH_1991__66_4_140228, author = {Pekka Tukia}, title = {Homomorphisms of constant stretch between {M\"obius} groups.}, journal = {Commentarii mathematici Helvetici}, pages = {155--168}, publisher = {mathdoc}, volume = {66}, number = {4}, year = {1991}, zbl = {0719.30035}, url = {http://geodesic.mathdoc.fr/item/CMH_1991__66_4_140228/} }
Pekka Tukia. Homomorphisms of constant stretch between Möbius groups.. Commentarii mathematici Helvetici, Tome 66 (1991) no. 4, pp. 155-168. http://geodesic.mathdoc.fr/item/CMH_1991__66_4_140228/