Amirov, R. K., B. Keskin, and G. Özkan. “Direct and Inverse Problems for the Dirac Operator With a Spectral Parameter Linearly Contained in a Boundary Condition”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 61, no. 9, Sept. 2009, pp. 1155-66, https://umj.imath.kiev.ua/index.php/umj/article/view/3088.