Savchuk, V. V., and S. O. Chaichenko. “Best Approximations for the Cauchy Kernel on the Real Axis”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 66, no. 11, Nov. 2014, pp. 1540–1549, https://umj.imath.kiev.ua/index.php/umj/article/view/2244.