2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/78260We show that there exist infinitely many commensurability classes of finite volume hyperbolic 3-manifolds whose fundamental group contains a subgroup which is locally free but not free. The main technical tool is the fact that a collection of hyperbolic 3-manifolds of bounded volume contains infinitely many commensurability classes. The result then by an application of Thurston's hyperbolization theorem for Haken 3-manifolds.14 pagesGeometric Topology57M50, 30F40, 20E25text