BartV. A., and KhavinV. P. “Szego-Kolmogorov-Krein Theorems on Weighted Trigonometrical Approximation and Carleman-Type Relations”. Ukrains’kyi Matematychnyi Zhurnal 46, no. 1-2 (February 25, 1994): 100–127. Accessed November 24, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/5773.