2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/148101$τ\toππν$, $τ\toπKν$, $τ\to Kην$, $τ\to 3πν$ and $τ\to ππKν$ have been investigated using chiral symmetry with dispersion relation in agreement with the unitarity condition.14 pages, latex, uuencoded file. Talk given at the International Symposium on Heavy Flavour and Electroweak Theory (Beijing, 95)High Energy Physics - Phenomenologytext