2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/40955We suggest two grand unified models where the fifth dimensional coordinate is compactified on an $S_1/(Z_2 \times Z_2')$ orbifold.Talk given at the Summer Institute 2001, Yamanashi, Japan, 13-20 Aug 2001High Energy Physics - PhenomenologyGrand Unified Models on $S_1/(Z_2 \times Z_2')$ Orbifoldtext