2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/78348We construct smooth 4-manifolds that are homeomorphic but not diffeomorphic to the "cusp" and the "fishtail", which are certain thickened singular 2-spheres.14 pages, 22 figuresGeometric TopologyAlgebraic Geometry57R10text