2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/69980There is a well-known problem about isospectrality of Riemannian manifolds: whether isospectral manifolds are isometric. In this work we give an answer to this problem for 3-dimensional compact flat manifolds.26 pages, 11 figuresDifferential GeometrySpectral Theory58J50; 58J32text