Kmit, I. Ya., L. Recke, and V. I. Tkachenko. 2013. “Robustness of Exponential Dichotomies of Boundary-Value Problems for General First-Order Hyperbolic Systems”. Ukrains’kyi Matematychnyi Zhurnal 65 (2), 236-51. https://umj.imath.kiev.ua/index.php/umj/article/view/2415.