@article{AFM_1996_21_2_a11,
     author = {F.W. Gehring and G.J. Martin},
     title = {On the {Margulis} constant for {Kleinian} groups, {I}},
     journal = {Annales Fennici Mathematici},
     pages = {439--462},
     publisher = {mathdoc},
     volume = {21},
     number = {2},
     year = {1996},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/AFM_1996_21_2_a11/}
}