1. V. K. Dzyadyk, Introduction to Theory of Uniform Approximation of Functions by Polynomials [in Russian], Nauka, Moscow (1977).
2. G. G. Lorentz and R. A. De Vore, Constructive Approximation, Berlin, New York (1993).
3. A. F. Timan, Theory of Approximations of Functions of Real Variable [in Russian], Fizmatgiz, Moscow (1960).
4. N. I. Akhiezer, Lectures on Approximation Theory [in Russian], Nauka, Moscow (1965).
5. Yu. A. Brudnyi, “On a theorem of local best approximations” [in Russian], In: Functional Analysis and Theory of Functions. II, p. 43–49, Kazan’ (1964).