Kuzhel’, S. A. “On Conditions for the Applicability of the Lax–Phillips Scattering Scheme to the Investigation of an Abstract Wave Equation”. Ukrains’kyi Matematychnyi Zhurnal 55, no. 5 (May 25, 2003): 621-630. Accessed May 17, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/3938.