%0 Journal Article
%A Tretkoff, Carol
%T Nonparabolic subgroups of the modular group
%J Glasgow mathematical journal
%D 1975
%P 91-102
%V 16
%N 2
%U http://geodesic.mathdoc.fr/articles/10.1017/S0017089500002573/
%R 10.1017/S0017089500002573
%F 10_1017_S0017089500002573