@article{ELMA_1974__29_141135,
     author = {O. Botsch},
     title = {Ein reduziertes {Erzeugenden-System} der {Kongruenzgruppe} in der {Ebene.}},
     journal = {Elemente der Mathematik},
     pages = {39--45},
     publisher = {mathdoc},
     volume = {29},
     year = {1974},
     zbl = {0274.50009},
     url = {http://geodesic.mathdoc.fr/item/ELMA_1974__29_141135/}
}