2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/78423We generalize the fundamental structure Theorem on Hopf (bi)-modules by Larson and Sweedler to quasi-Hopf algebras H. If H is finite dimensional this proves the existence and uniqueness (up to scalar multiples) of integrals in H. Among other applications we prove a Maschke type Theorem for diagonal crossed products as constructed by the authors.28 pages, amstex, formula at the end of section 6 correctedQuantum Algebratext