2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/64164We determine the necessary and sufficient conditions on the entries of the intersection matrix of the transcendental lattice of a K3 surface for the K3 surface to doubly cover an Enriques surface.LaTeX2e,14 pagesAlgebraic Geometry14J28;11E39text