GorbachukV. I., and GorbachukM. L. “Behavior of the Extended Spectral Measure of a Self-Adjoint Operator at Infinity”. Ukrains’kyi Matematychnyi Zhurnal 49, no. 4 (April 25, 1997): 510–516. Accessed November 24, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/5024.