DeinekaV. S., and SergienkoI. V. “Problems of Transmission With Inhomogeneous Principal Conjugation Conditions and High-Accuracy Numerical Algorithms for Their Discretization”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 54, no. 2, Feb. 2002, pp. 258-75, https://umj.imath.kiev.ua/index.php/umj/article/view/4061.