2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/42651In the framework of the three-neutrino mixing the neutrino oscillations in the atmospheric and solar ranges of neutrino mass-squared differences are considered in the leading approximation. Neutrinoless double $β$- decay is also discussed.Report at the Ist Yamada Symposium on neutrinos and Dark Matter in Nuclear Physics, June 9-14, 2003, Nara, JapanHigh Energy Physics - Phenomenologytext