Kostova, V. A. “An Exact Estimate in the Theory of Approximation of the Function \(x^\alpha\) With Bernstein Polynomials in Hausdorff Metric”. Anal. Numér. Théor. Approx., vol. 16, no. 2, Aug. 1987, pp. 133-40, https://ictp.acad.ro/jnaat/journal/article/view/1987-vol16-no2-art6.