@article{GT_2008_12_1_a13,
     author = {Sambusetti, Andrea},
     title = {Asymptotic properties of coverings in negative curvature},
     journal = {Geometry & topology},
     pages = {617--637},
     publisher = {mathdoc},
     volume = {12},
     number = {1},
     year = {2008},
     doi = {10.2140/gt.2008.12.617},
     url = {http://geodesic.mathdoc.fr/articles/10.2140/gt.2008.12.617/}
}