2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/60363We use the new categories of spectra and MU-modules constructed by Elmendorf, Kriz, Mandell and May to get improved results about multiplicative structures on spectra such as P(n) and E(n), particularly in the case p=2.31 pages; one included postscript figureAlgebraic Topology55T25text