1. Wiener, N., “The Fourier Integral and Certain of its Applications”, Chapter 4 (Camb. Univ. Press, 1933). For further developments, cf. Wiener, N., and Wintner, A., J. Math. and Phys. (M.I.T.), 17, 233 (1939); and Wiener, N., and Wintner, A., Amer. J. Math., 63, 796 (1941).
2. Wiener, N., Acta Math., 55, 117 (1930).
3. Birkhoff, G. D., Proc. U.S. Nat. Acad. Sci., 17, 650 (1931).
4. Lévy, P., Compositio Math., 7, 283 (1939).