V. L. Ostrovsky and Y. S. . Samoilenko, “Application of the projectional spectral theorem to non-commutating operators families”, Ukr. Mat. Zhurn., vol. 40, no. 4, pp. 469–481, Jun. 1988, Accessed: Dec. 07, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/9182