BOZHOK, R. V.; KOSHMANENKO, V. D. Singular Perturbations of Self-Adjoint Operators Associated with Rigged Hilbert Spaces. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 57, n. 5, p. 622–632, 2005. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/3628. Acesso em: 5 dec. 2025.