Dorogovtsev, A.Y. (1993) “On periodic and bounded solutions of the operator Riccati equation”, Ukrains’kyi Matematychnyi Zhurnal, 45(2), pp. 239–242. Available at: https://umj.imath.kiev.ua/index.php/umj/article/view/5804 (Accessed: 14 April 2025).