“…cannot be correctly approached if the inclusion interactions are ignored, except where concentrations are ''dilute enough" (Willis and Acton, 1976;Christensen, 1979). For ''high" concentrations, the isolated (one site) inclusion approximation has been significantly improved by using either the solution for the pair interaction problem between two ellipsoids (Berveiller et al, 1987;Kouris and Tsuchida, 1991;Anttreter and Fisher, 1996) or statistical estimates that are based on correlation functions of rank two and more (Davis, 1991;Helsing, 1993;Ponte Castaneda and Willis, 1995;Kanaun, 2003). However, when inclusions are not homogeneously or randomly distributed within a matrix, the estimate of the cluster or pattern effects needs to approach some mean, or effective, interaction contribution in the arrangement (De Bartolo and Hillberry, 1998;Estevez et al, 1995Estevez et al, , 1999.…”