1. S. B. Stechkin, “An extremum problem for trigonometric series with nonnegative coefficients,”Acta. Math. Acad. Sci. Hung.,23, No. 3,4, 289–291 (1972).
2. S. V. Konyagin, “On the distribution of the fractional parts of terms of some geometric progressions,” in:II International Conference “Algebraic, Probabilistic, Geometric, Combinatorial, and Functional Methods in Number Theory. Abstracts of Reports [in Russian], Voronezh State University, Voronezh (1995), p. 89.
3. E. Stein and G. Weiss,Introduction to Fourier Analysis on Euclidean Spaces, Princeton (1971).
4. J.-P. Kahane,Séries de Fourier absolument convergentes, Springer-Verlag, Heidelberg (1970).
5. A. Zygmund,Trigonometric Series, 2nd ed., Cambridge Univ. Press, Cambridge (1959).