2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/162259The maximal index of a Euclidean lattice L of dimension n is the maximal index of the sub-lattices of L spanned by n independent minimal vectors of L. In this paper, we prove that a perfect lattice of maximal index two not provided by a cross-section has dimension at most 5.25 pagesNumber Theory11H55text