2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/148770Let $X$ be an oriented 4-manifold which does not have simple SW-type, for example a blow-up of a rational or ruled surface. We show that any two cohomologous and deformation equivalent symplectic forms on $X$ are isotopic. This implies that blow-ups of these manifolds are unique, thus extending work of Biran. We also establish uniqueness of structure for certain fibered 4-manifolds.Latex 16 pages. Revised version of Aug 4, 1997. The last section on symplectic fibrations has been improvedDifferential Geometry53C15 (Primary) 57R57 (Secondary)text