@article{GT_2009_13_5_a9,
     author = {Bowen, Lewis},
     title = {Free groups in lattices},
     journal = {Geometry & topology},
     pages = {3021--3054},
     publisher = {mathdoc},
     volume = {13},
     number = {5},
     year = {2009},
     doi = {10.2140/gt.2009.13.3021},
     url = {http://geodesic.mathdoc.fr/articles/10.2140/gt.2009.13.3021/}
}