“…Following Cosserat theory, a number of higher-order continuum models were developed by Mindlin (1964), Sun et al (1968), Herrmann and Achenbach (1968). More recently, similar approaches were adopted to describe the propagation of nonlinear strain waves in miscrostructured solids (Engelbrecht et al, 2007(Engelbrecht et al, , 2011Porubov et al, 2004Porubov et al, , 2009Randrüüt and Braun, 2010). A recent review of the modelling of heterogeneous media in terms of internal variables was presented by Berezovski et al (2011a, b).…”