V. I. Gorbachuk and M. L. Gorbachuk, “Behavior of the extended spectral measure of a self-adjoint operator at infinity”, Ukr. Mat. Zhurn., vol. 49, no. 4, pp. 510–516, Apr. 1997, Accessed: Feb. 17, 2026. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/5024