2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/48917It is shown that the Super-Kamiokande atmospheric up--down asymmetry, together with the results of all other neutrino oscillation experiments, allows to constraint the possible spectra of four massive neutrinos. The two schemes with two pairs of neutrinos with close masses separated by a gap of about 1 eV are favored by the data.7 pages. Talk presented by C. Giunti at WIN99, Cape Town, South Africa, 24-30 January 1999High Energy Physics - Phenomenologytext