@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/