@article{MZ_1959__72_183615,
     author = {Wilhelm Specht},
     title = {Freie {Untergruppen} der bin\"aren unimodularen {Gruppe.}},
     journal = {Mathematische Zeitschrift},
     pages = {319--331},
     year = {1959},
     volume = {72},
     zbl = {0091.02901},
     url = {http://geodesic.mathdoc.fr/item/MZ_1959__72_183615/}
}