TY  - JOUR
AU  - Mason, A. W.
TI  - Lattice subgroups of free congruence groups
JO  - Glasgow mathematical journal
PY  - 1969
SP  - 106
EP  - 115
VL  - 10
IS  - 2
UR  - http://geodesic.mathdoc.fr/articles/10.1017/S0017089500000641/
DO  - 10.1017/S0017089500000641
ID  - 10_1017_S0017089500000641
ER  -