1. Golubov, B., Efimov, A., and Skvortsov, V.: Walsh series and transforms, Kluwer Acad. Publ., 1991. (Translated from the Russian.)
2. Levizov, S.V.: ‘Some properties of the Walsh system’, Mat. Zametki
27 (1980), 715–720. (In Russian.)
3. Price, J.J.: ‘Orthonormal sets with non-negative Dirichlet kernels, II’, Trans. Amer. Math. Soc.
100 (1961), 153–161.
4. Schipp, F., Wade, W.R., and Simon, P.: Walsh series; an introduction to dyadic harmonic analysis, A. Hilger, 1990.
5. Golubov, B., Efimov, A., and Skvortsov, V.: Walsh series and transforms, Kluwer Acad. Publ., 1987. (Translated from the Russian.)