RadzievskiiG. V. “Uniqueness of Solutions of Boundary-Value Problems for Operator-Differential Equations on a Finite Segment and on a Semiaxis”. Ukrains’kyi Matematychnyi Zhurnal 46, no. 3 (March 25, 1994): 279–292. Accessed July 27, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/5761.