DÍAZ, Pablo A. Absolutely continuous spectrum preservation: A new proof for unitary operators under finite-rank multiplicative perturbations. CUBO, A Mathematical Journal, [S. l.], v. 27, n. 3, p. 701–712, 2025. DOI: 10.56754/0719-0646.2703.701. Disponível em: https://cubo.ufro.cl/index.php/cubo/article/view/4198. Acesso em: 27 dec. 2025.