2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/10209Review paper presented at the meeting "Formation of the Galactic Halo: Inside and Out", Tucson, October 1995.14 pages compressed uuencoded Postscript. Also available at http://www.dao.nrc.ca/DAO/SCIENCE/science.htmlAstrophysicstext