BelyV. I., and StrelkovskayaI. V. “Approximation of Functions by Analytical Complex Splines in the Regions With Quasi-Conformal Boundary ”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 40, no. 5, Aug. 1988, pp. 563-8, https://umj.imath.kiev.ua/index.php/umj/article/view/8803.