HrabovaU. Z., KalchukI. V., and StepanyukT. A. “Approximation of Functions from the classes $W_{β}^r H^{α }$ by Weierstrass Integrals”. Ukrains’kyi Matematychnyi Zhurnal 69, no. 4 (April 25, 2017): 510-519. Accessed November 27, 2020. http://umj.imath.kiev.ua/index.php/umj/article/view/1712.