2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/189403We provide the general tadpole conditions for a class of supersymmetric orientifold models by studing the general properties of the elements included in the orientifold group. In this talk, we concentrate on orientifold models of the type $T^6/Z_M\times Z_N$.8 pages, 1 figure, Latex2e. Proceedings of RTN Workshop on the Quantum Structure of Space-time and the Geometric Nature of Fundamental Interactions and EXT Workshop on Fundamental Interactions and the Structure of Spacetime, Kolymbari, Crete, Greece, 5-10 Sep 2004High Energy Physics - Theorytext