@article{01436126, title = {Some linear groups virtually having a free quotient.}, journal = {Journal of Lie Theory}, volume = {10}, year = {2000}, pages = {171-180}, zbl = {0958.22008}, language = {en}, url = {http://dml.mathdoc.fr/item/01436126} }
Margulis, G.A.; Vinberg, È.B. Some linear groups virtually having a free quotient.. Journal of Lie Theory, Tome 10 (2000) pp. 171-180. http://gdmltest.u-ga.fr/item/01436126/