1. I. N. Pak, ‘‘On the sums of trigonometric series,’’ Russ. Math. Surv. 35, 105–168 (1980). https://doi.org/10.1070/RM1980v035n02ABEH001631
2. Ph. Hartman and A. Wintner, ‘‘On sine series with monotone coefficients,’’ J. London Math. Soc. s1-28, 102–104 (1953). https://doi.org/10.1112/jlms/s1-28.1.102
3. A. Zygmund, Trigonometric Series (Cambridge Univ. Press, New York, 1959).
4. G. H. Hardy and W. W. Rogosinski, Fourier Series (Dover, Mineola, N.Y., 1999).
5. Über das Vorzeichen gewisser trigonometrischer Summen;L. Vietoris,1958