2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/43987The present status of the problem of identifying the sign of $Δm_{12}^2$ is discussed in view of the development of new methods of detection of solar neutrinos.3 pages, some extention and minor corrections, one reference addedHigh Energy Physics - PhenomenologyAbout the sign of $Δm_{12}^2$text