%0 Journal Article
%A A.W. Mason
%T Free Quotients of Congruence Subgroups of SL2 Over a Coordinate Ring.
%J Mathematische Zeitschrift
%D 1988
%P 39-52
%V 198
%N 3
%I mathdoc
%U http://geodesic.mathdoc.fr/item/MZ_1988__198_3_173908/
%F MZ_1988__198_3_173908