2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/45457We discuss the difficulties that arise when one tries to calculate $δρ$ using dispersion relations.4 pages, LATEX, style file appended. Talk presented at "Beyond the Standard Model IV", Lake Tahoe, CA, Dec. 13-18, 1994High Energy Physics - Phenomenologytext