aDICAM, Group of Solid and Structural Mechanics, Univ

formed by a variety of materials (Horgan and Knowles, 1983), both in statics and dynamics. for linear elastic pioneerin been exte studied in subsequent research (see e.g. Gurtin, 1972; and Knowles, 1983). In particular, early work of Toupin yielded an exponential spatial decay estimate of the stored for a cylindrical semi-infinite solid, although other forms of the Saint-Venant principle have been stated (Horgan and Knowles, 1983; Horgan, 1989, 1996). Some results have been given also for linear viscoelastic materials (Chirita et al., 1997 and references therein) for both the inertial and the quasi-static case; for a sys-tematic and in-depth discussion of certain aspects of this topic, see Amendola et al. (2012), chapter 20. q Our thanks to M. Fabrizio for useful conversations on aspects of this paper