@article{MAN_1931__105_159530,
     author = {St. Pietrkowski},
     title = {Untergruppen und {Quotientengruppen} unendlicher {Abelscher} {Gruppen}},
     journal = {Mathematische Annalen},
     pages = {666--671},
     publisher = {mathdoc},
     volume = {105},
     year = {1931},
     zbl = {0003.10003},
     url = {http://geodesic.mathdoc.fr/item/MAN_1931__105_159530/}
}