2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/3367We present preliminary results of an investigation of the clustering properties of high matter density peaks between redshift ~2 and ~3, as traced by Lyman limit and Damped Ly-alpha systems in spectra of close QSO pairs and groups.2 pages, 1 figure, to appear in the Proceedings of the XVII IAP Colloquium "Gaseous Matter in Galaxies and Intergalactic Space"Astrophysicstext