1. See, for instance, E. H. Lee, Viscoelastic stress analysis, Proc., First Symposium on Naval Structural Mechanics, Pergamon, New York, 1960, p. 456
2. A definition of stable inelastic material;Drucker, D. C.;J. Appl. Mech.,1959
3. M. Loève, Probability theory. Van Nostrand, New York 1955, p. 207
4. E. C. Titchmarsh, Introduction to the theory of Fourier integrals, Oxford, 1948
5. O. D. Kellog, Foundations of potential theory, Dover, New York, 1953, p. 118