@article{MZ_1959__71_169809,
     author = {Walter Roelcke and Max Koecher},
     title = {Diskontinuierliche und diskrete {Gruppen} von {Isometrien} metrischer {R\"aume.}},
     journal = {Mathematische Zeitschrift},
     pages = {258--267},
     publisher = {mathdoc},
     volume = {71},
     year = {1959},
     zbl = {0092.02804},
     url = {http://geodesic.mathdoc.fr/item/MZ_1959__71_169809/}
}