2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/56824We briefly review the main aspects of (Poincaré-Dulac) normal forms; we have a look at the non-uniqueness problem, and discuss one of the proposed ways to ``further reduce'' the normal forms. We also mention some convergence results.standard LaTeX, 20 pagesMathematical PhysicsDynamical Systems70K45text