1. A. F. Timan, Theory of Approximation of Functions of a Real Variable (Fizmatlit, Moscow, 1960) [in Russian].
2. N. I. Akhiezer, Lectures in the Theory of Approximation (Nauka, Moscow, 1965) [in Russian].
3. R. M. Trigub, “The constructive characteristics of certain classes of functions,” Izv. Akad. Nauk SSSR Ser. Mat. 29 (3), 615–630 (1965).
4. G. A. Fomin, “On linear methods for the summability of Fourier series that are similar to the Bernshtein– Rogosinski method,” Math. USSR-Izv. 1 (2), 319–333 (1967).
5. R. Trigub, “Norms of linear functionals, summability of trigonometric Fourier series and Wiener algebras,” in Operator Theory and Harmonic Analysis, Springer Proc. in Math. Stat. (Springer, Cham, 2020), Vol. 357, pp. 549–568.