2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/46308We summarize the current status of our understanding of the structure of the perturbative QCD expressions for the QCD generalization of the Crewther relation.22 pages, LATEX; Invited talk at the Workshop ``Continuous Advances in QCD'', Minneapolis, March 28-31, 1996; to be published in the ProceedingsHigh Energy Physics - Phenomenologytext