Kuzhel’, S. A. and Patsyuk, O. M. (2012) “On the theory of $\mathcal{PT}$-symmetric operatorss”, Ukrains’kyi Matematychnyi Zhurnal, 64(1), pp. 32-49. Available at: https://umj.imath.kiev.ua/index.php/umj/article/view/2554 (Accessed: 19April2024).