1. V. K. Dzydyk, Introduction to the Theory of Uniform Approximation of Functions by Means of Polynomials [in Russian], Nauka, Moscow (1977).
2. S. M. Nikol'skii, ?On optimal approximation of functions that satisfy a Lipschitz condition by means of polynomials,? Izv. Akad. Nauk SSSR, Ser. Mat.,10, 295?317 (1946).
3. V. K. Dzydyk, ?On a constructive description of functions that satisfy the condition Lip ?(0 < ? < 1) on a finite interval of the real axis,? Izv. Akad. Nauk SSSR, Ser. Mat.,20, 623?642 (1956).
4. A. F. Timan, ?Strenthening Jackson's theorem on optimal approximation of continuous functions by polynomials on a finite interval of the real axis,? Dokl. Akad. Nauk SSSR,78, 17?20 (1951).
5. V. K. Dzydyk, ?Nikol'skii problem in a complex domain,? Izv. Akad. Nauk SSSR, Ser. Mat.,23, No. 5, 697?736 (1959).