Bart, V. A., and V. P. Khavin. “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 December 6, 2025. https://umj.imath.kiev.ua/index.php/umj/article/view/5773.