@article{MZ_1986__191_173654,
     author = {F. Rudolf Beyl},
     title = {The {Schur} {Multiplicator} of {SL(2,} {Z/mZ)} and the {Congruence} {Subgroup} {Property.}},
     journal = {Mathematische Zeitschrift},
     pages = {23--42},
     publisher = {mathdoc},
     volume = {191},
     year = {1986},
     zbl = {0581.20050},
     url = {http://geodesic.mathdoc.fr/item/MZ_1986__191_173654/}
}