1. N.G. McGrum, B.E. Read, and G. Williams, in: Anelastic and Dielectric Effects in Polymeric Solids, John Wiley and Sons, London, pp. 38, 141.
2. U.T. Kreibich, F. Lohse, and R. Schmid, in: Nonmetallic Materials and Composites at Low Materials and Composites at Low Temperatures, Plenum Press New York (1979), p. 1.
3. N. Brown, in: Microplasticity, Interscience Publishers, John Wiley and Sons, p. 71.
4. H.J. Schladitz, Z. Metallkd. 59, 18 (1968)