BelyV. I., and StrelkovskayaI. V. 1988. “Approximation of Functions by Analytical Complex Splines in the Regions With Quasi-Conformal Boundary ”. Ukrains’kyi Matematychnyi Zhurnal 40 (5), 563-68. https://umj.imath.kiev.ua/index.php/umj/article/view/8803.