[1]
M. Y. Dudkin, “Invariant symmetric restrictions of a self-adjoint operator. II”, Ukr. Mat. Zhurn., vol. 50, no. 6, pp. 781–791, Jun. 1998, Accessed: Apr. 16, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/4888