Hrod, A. I., and S. A. Kuzhel’. 2013. “Scattering Theory for 0-Perturbed $\mathcal{P}\mathcal{T}$ -Symmetric Operators”. Ukrains’kyi Matematychnyi Zhurnal 65 (8), 1059–1079. https://umj.imath.kiev.ua/index.php/umj/article/view/2490.