1. The functions which operate on Fourier transforms;Helson, Henry;Acta Math.,1959
2. Some properties of trigonometric series whose terms have random signs;Salem, R.;Acta Math.,1954
3. H. S. Shapiro, Extremal problems for polynomials and power series, Thesis for S. M. Degree, Massachusetts Institute of Technology, 1951.
4. Antoni Zygmund, Trigonometrical series, Warsaw, 1935.