2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/60306We reprove and strengthen some old difficult theorems of 4-manifolds by the aid of recently discovered modern tools, which involve contact structures on 3-manifolds, compact Stein domains, etc.LaTeX2e, 8 pages, 9 figures. Slightly modified version of the article appeared in Turkish J. of MathGeometric TopologySymplectic Geometry57M50; 32E10text