2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/105923The light neutrino mass spectrum and mixing matrix of seesaw model including three right-handed neutrinos are studied for the most general case. An approximate formulae for mass eigenvalues, mixing matrix, and CP violation of neutrino oscillations are given.7 pages, no figures. The paper is prepared as a contribution to the Symposium in Honour of Professor Gustavo C. Branco, CP Violation and Flavour PuzzleHigh Energy Physics - Phenomenologytext