2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/198698Recent atmospheric neutrino data at Super-Kamiokande suggest the large flavor mixing of neutrinos. Models for the lepton mass matrix, which give the near-maximal flavor mixing, are discussed in the three family model. Especially, details of the models with the $S_3$ or O(3) flavor symmetry are studied.16 pages, latex, some references are addedHigh Energy Physics - Phenomenologytext