1. A. Beurling and H. Helson, “Fourier-Stieltjes transforms with bounded powers,” Math. Scand., 1 (1953), 120–126.
2. B. Green and S. Konyagin, “On the Littlewood problem modulo a prime,” Canad. J. Math., 61:1 (2009), 141–164.
3. A. Zygmund, Trigonometric Series, vol. 2, Cambridge University Press, Cambridge, 1959.
4. J.-P. Kahane, “Transformées de Fourier des fonctions sommables,” in: Proc. Internat. Congr. Math., 1962, Inst. Mittag-Leffler, Djursholm, 1963, 114–131.
5. J.-P. Kahane, Séries de Fourier absolument convergenntes, Springer-Verlag, Berlin, 1970.