2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/103475We extend the string model building rules for the construction of chiral supersymmetric Type I compactifications on smooth Calabi-Yau manifolds. These models contain stacks of D9-branes endowed with general stable U(n) bundles on their world-volume and D5-branes wrapping holomorphic curves on the Calabi-Yau.12 pages, LATEX, contribution to the proceedings "II. Southeastern European Workshop Challenges Beyond The Standard Model", 19-23 May 2005, Vrnjacka Banja, Serbia; v2: one ref. addedHigh Energy Physics - Theorytext