2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/58099We present remarkable properties of the groups SL2(Z/NZ) which might be useful in detailed studies of some quotients appearing in Conformal Field Theories.7 pages, dedicated to the memory of C. ItzyksonMathematical PhysicsConformal Field Theories on the Two-Torus and Quotients of SL2(Z)text