@article{MAN_1883__22_157087,
     author = {Gierster},
     title = {Ueber {Congruenzgruppen} von {Primzahlstufe}},
     journal = {Mathematische Annalen},
     pages = {177--189},
     publisher = {mathdoc},
     volume = {22},
     year = {1883},
     language = {de},
     url = {http://geodesic.mathdoc.fr/item/MAN_1883__22_157087/}
}