2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/41949Recent work on analytical solutions to the MSW equations for three neutrino flavours is reviewed, with emphasis on the exponential density. Application to a particular mass matrix, proposed by Lehmann, Newton and Wu, is also discussed. Within this model, the experimental data allow a determination of the three neutrino masses. They are found to be 0.002-0.004, 0.01 and 0.05 eV.6 pages, LaTeX, 1 figure. Invited talk given at the conference "Beyond the Desert 2002", 2-7 June 2002, Oulu, Finland, to be published in the proceedingsHigh Energy Physics - Phenomenologytext