@article{JLT_1999_9_2_a3,
     author = {H. Abels},
     title = {Discrete {Groups} of {Affine} {Isometries}},
     journal = {Journal of Lie theory},
     pages = {321--35},
     year = {1999},
     volume = {9},
     number = {2},
     url = {http://geodesic.mathdoc.fr/item/JLT_1999_9_2_a3/}
}