V. S. Romanyuk, “Estimates of the Kolmogorov Widths of Classes of Analytic Functions Representable by Cauchy-Type Integrals. I”, Ukr. Mat. Zhurn., vol. 53, no. 2, pp. 229–237, Feb. 2001, Accessed: Feb. 16, 2026. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/4238