@article{PMIHES_1979__50__171_0, author = {Sullivan, Dennis}, title = {The density at infinity of a discrete group of hyperbolic motions}, journal = {Publications Math\'ematiques de l'IH\'ES}, pages = {171--202}, publisher = {Institut des Hautes \'Etudes Scientifiques}, volume = {50}, year = {1979}, zbl = {0439.30034}, mrnumber = {81b:58031}, language = {en}, url = {http://www.numdam.org/item/PMIHES_1979__50__171_0/} }