2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/58709Some properties of non-orientable 3-manifolds are shown. The semi-group of cobordism of immersions of surfaces in such manifolds is computed and proven actually to be a group. Explicit invariants are provided.30 pages, 13 figuresGeometric Topology57R90, 57R42text