2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/67916This is the written version of my five lectures at the Banach Center mini-school on "Schubert Varieties", in Warsaw, May 18-22, 2003.25 pages, LaTeX, 8 figuresAlgebraic Geometry14N35 (Primary) 14M15, 14N15, 05E15 (Secondary)text