@article{10_4007_annals_2009_170_123,
     author = {Frederick W. Gehring and Gaven J. Martin},
     title = {Minimal co-volume hyperbolic lattices, {I:}  {The} spherical points of a {Kleinian} group},
     journal = {Annals of mathematics},
     pages = {123--161},
     publisher = {mathdoc},
     volume = {170},
     number = {1},
     year = {2009},
     doi = {10.4007/annals.2009.170.123},
     mrnumber = {2521113},
     zbl = {1171.30014},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4007/annals.2009.170.123/}
}