Dovgoshei, A. A. “Chebyshev Polynomial Approximation on a Closed Subset With Unique Limit Point and Analytic Extension of Functions”. Ukrains’kyi Matematychnyi Zhurnal, vol. 48, no. 7, July 1996, pp. 891-00, https://umj.imath.kiev.ua/index.php/umj/article/view/5261.