2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/3529Comparison of the observed evolution of the Ly-alpha transmitted flux in the spectra of four highest redshift quasars discovered by SLOAN survey with the theoretical prediction for this evolution based on the state-of-the-art numerical simulations of cosmological reionization already allows one to constrain the redshift of reionization to z = 6.2 +- 0.1s +- 0.2r, where systematic and random errors are given respectively.Submitted to MNRAS pink pagesAstrophysicstext