@article{GDZPPN002208628,
title = {Inequalities for M\"obius transformations and discrete groups.},
journal = {Journal f\"ur die reine und angewandte Mathematik},
volume = {416},
year = {1991},
pages = {31-76},
zbl = {0722.30034},
url = {http://dml.mathdoc.fr/item/GDZPPN002208628}
}
Martin, G.J.; Gehring, F.W. Inequalities for Möbius transformations and discrete groups.. Journal für die reine und angewandte Mathematik, Tome 416 (1991) pp. 31-76. http://gdmltest.u-ga.fr/item/GDZPPN002208628/