1. See T. Alfrey,Mechanical Behavior of High Polymers(Interscience Publishers, Inc., New York, 1948) as a general reference on the use of mechanical models of viscoelastic materials and especially Appendices II and III in which are summarized Alfrey’s investigations of homogeneous and non-homogeneous stress and strain in a very general viscoelastic medium.
2. For the dyadic notation used in this paper, see C. E. Weatherburn,Advanced Vector Analysis(G. Bell and Sons, London, 1928).
3. E. G. Coker and L. N. G. Filon,A Treatise on Photo-Elasticity(Cambridge University Press, London, 1932), p. 17.
4. See reference 1, p. 561, for comparison.
5. See reference 3, p. 256.