@article{02124383,
title = {Tits geometry, arithmetic groups, and the proof of a conjecture of Siegel.},
journal = {Journal of Lie Theory},
volume = {14},
year = {2004},
pages = {317-338},
zbl = {1086.53073},
language = {en},
url = {http://dml.mathdoc.fr/item/02124383}
}
Leuzinger, Enrico. Tits geometry, arithmetic groups, and the proof of a conjecture of Siegel.. Journal of Lie Theory, Tome 14 (2004) pp. 317-338. http://gdmltest.u-ga.fr/item/02124383/