%0 Journal Article
%A R.A. RANKIN
%T Lattice Subgroups of Free Congruence Groups.
%J Inventiones mathematicae
%D 1966
%P 215-221
%V 2
%I mathdoc
%U http://geodesic.mathdoc.fr/item/IM_1966__2_141853/
%F IM_1966__2_141853