1. Babenko, K.I.: Izv. Akad. Nauk SSSR. Ser. Mat.25, 531 (1961)
2. Beckner, W.: Proc. Nat. Acad. Sci. U.S.A.72, 638 (1975)
3. Gross, L.: Logarithmic Sobolev Inequalities (to appear in Amer. J. of Math)
4. Bialynicki-Birula, I., Mycielski, J.: Wave equations with logarithmic nonlinearities. Bull. Acad. Polon. Sci. Cl. III.23, 461 (1975)
5. Zygmund, A.: Trigonometric series, Vol. II, p. 101. Cambridge University Press 1959