@article{IM_1968__6_141941,
     author = {E. THOMA},
     title = {Eine {Charakterisierung} diskreter {Gruppen} vom {Typ} {I.}},
     journal = {Inventiones mathematicae},
     pages = {190--196},
     publisher = {mathdoc},
     volume = {6},
     year = {1968},
     zbl = {0169.03802},
     url = {http://geodesic.mathdoc.fr/item/IM_1968__6_141941/}
}