2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/40636Neutrino flavors, light and heavy, are discussed in their interdependence within the minimal unifying gauge group of SO10. The general situation which excludes the existence of an {\it exact} symmetry from which {\it exactly} vanishing light neutrino masses would follow is discussed. {\it Subtle} and {\it simple} consequences for 'low-low' oscillation phenomena are presented in a general framework.14 pages, no figuresHigh Energy Physics - Phenomenologytext