2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/59595Conference matrices are used to define complex structures on real vector spaces. Certain lattices in these spaces become modules for rings of quadratic integers. Multiplication of these lattices by non-principal ideals yields simple constructions of further lattices including the Leech lattice.17 pages. Subitted to European Journal of CombinatoricsNumber TheoryCombinatorics11H71 (Primary) 105B20, 94B15 (Secondary)text