@article{JRAM_1978__301_152015,
     author = {Hans-Jochen Bartels},
     title = {Definite arithmetische {Gruppen.}},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {27--29},
     publisher = {mathdoc},
     volume = {301},
     year = {1978},
     zbl = {0376.12004},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1978__301_152015/}
}