I express my full indebtedness to all researchers whose work is referenced in this book. Without their outstanding contributions to knowledge, this book would not have been written. I convey my thanks to Professor D. R. Axelrad (McGill University), who was the first person to introduce the fascinating subject of rheology to me and to Professor J. T. Pindera (University of Waterloo) for his kind encouragement and stimulating discussions on the subject matter. I am indebted to Dr J. H. Gittus, Editor-in-Chief Res Mechanica, for originally inviting me to write a book on viscoelasticity. of Permission granted to the author for the reproduction of figures and/or data by the following scientific societies, journals and publishers is gratefully acknowledged: Academic Press, American Chemical Society, American Institute of Physics, British Textile Technology Group, Elsevier Applied Science Publishers, Gebriider Born­ traeger, Helvetica Chimica Acta, Hermann, International Union of Crystallography, John Wiley & Sons, Pergamon Press, Springer-Verlag Heidelberg, Steinkopff Verlag, Tappi Journal, Taylor and Francis Ltd . . and the Institute of Physics. In the same context, the author wishes to express his sincere thanks and gratitude to Professors M. F. Ashby (University of Cambridge, United Kingdom), N. Davis (The Pennsylvania State University), H. F. Frost (Thayer School of Engineering), F. A. Leckie (University of Illinois at Urbana-Champaigne), E. H. Lee (Stanford University), J. M. Morrison (AT & T Bell Laboratories), A. K. Mukherjee (University of California, Davis) and Dr H. J. Sutherland (Sandia National Laboratories).