2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/112850This paper has been withdrawn. Counterexamples to the announced theorem can be made by observing that the natural map Ext(M,N)--> Ext(Lie(N),Lie(M)) is surjective and that the extension of two pure motives of the same weight is again pure. The proof contains a crucial mistake in the analysis of the ``glueing'' of trivialisations.This paper has been withdrawnNumber Theory11G09text