Free subgroups and normal subgroups of the modular group
Free subgroups and normal subgroups of the modular group
MonRs NEWMANIn this note we wish to point out some easy consequences of the Kurog subgroup theorem applied to the modular group F, which yield information of interest about free subgroups and normal subgroups of F.Here F is the group of 2 X 2 rational integral matrices of determinant 1 …