MOTOVILOV, A. K.; SHKALIKOV, A. A. Unconditional bases of subspaces related to non-self-adjoint perturbations of self-adjoint operators. Eurasian Mathematical Journal, [S. l.], v. 8, n. 1, p. 119–127, 2017. Disponível em: https://emj.enu.kz/index.php/main/article/view/658. Acesso em: 3 jan. 2026.