2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/49832Some applications of simple current techniques and fixed point resolution to theories of open strings are discussed. In addition to a brief review of work presented in two recent papers with L. Huiszoon and N. Sousa, some new results concerning uniqueness of crosscap coefficients are presented, as well as a strange sum rule for the modular matrix implied by the existence of crosscaps.21 pages, Latex. Invited talk at the Wigner Symposium, 16-22 August 1999, Istanbul, TurkeyHigh Energy Physics - Theorytext