[1]
M. Y. Dudkin, “Invariant symmetric restrictions of a self-adjoint operator. I”, Ukr. Mat. Zhurn., vol. 50, no. 5, pp. 623–631, May 1998, Accessed: Dec. 06, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/4900