2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/169055This paper has been withdrawn by the authors, due to the requirement of the Journal where a modified version will be published.This paper has been withdrawnFunctional Analysis43A85; 22E30A Theorem of Beurling and Hörmander on Damek-Ricci Spacestext