2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/185681An algebraic proof of the Gluing Theorem at tree level of perturbation theory in String Field Theory is given. Some applications of the theorem to closed string non-polynomial action are briefly discussed11 LaTex pagesHigh Energy Physics - TheoryOperator approach to the Gluing Theorem in String Field Theorytext