2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/198582I report on some recent work done in collaboration with E. de Rafael on the connection between ultraviolet renormalons in QCD and Nambu-Jona-Lasinio-like Lagrangians as its effective description at low energies.6 pages, LateX, espcrc2; contribution to QCD97, Montpellier, France, July 1997, to appear in the proceedingsHigh Energy Physics - Phenomenologytext