2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/219945The expressions for the superfluid density have been discussed in both weak and strong coupling approaches. The numerical calculations of temperature and isotope composition dependencies have been performed for a number of High-Tc compounds. The tight-binding parameters and corresponding Fermi surfaces are taken in accord to the available photoemission data.3 pages, 2 figures, corrected version of paper in Conference Proceedings of 3rd International Conference "Fundamental Problems of High Temperature Superconductivity" (FPS'08), P.N.Lebedev Physical Institute of the Russian Academy of Sciences, Moscow-Zvenigorod, October 13-17, 2008. Corrected typos, reference [3] modified, formula (5) modifiedSuperconductivitytext