2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/149326We review the basic principles of the construction of open and unoriented superstring models and analyze some representative examples.22 pages, Latex, 5 figures, Talk Presented at the "IV Italian-Korean Meeting on Relativistic Astrophysics", Rome-Gran Sasso-Pescara, July 1995; Two references addedHigh Energy Physics - Theorytext