2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/108871Let A be a unital C*-algebra. We shall introduce involutive A-A-equivalence bimodules and prove that any C*-algebra containing A with Watatani index 2 is constructed by an involutive A-A-equivalence bimodule.20 pages, to appear in J. Operator TheoryOperator Algebras46L08Involutive equivalence bimodules and inclusions of C*-algebras with Watatani index 2text