2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/224939In this note, we study some properties of the filtration of the Steenrod algebra defined from the excess of admissible monomials. We give several conditions on a cocommutative graded Hopf algebra A^* which enable us to develop the theory of unstable A^*-modules.This is the version published by Geometry & Topology Monographs on 18 April 2007Algebraic Topology55S10text