()          et al.  Proof: Remark:
S T V W min max LS LS[#1] LS[#1] Int Bdy k_- k_+ k_s i(r - t) i(r - t) i(z - t)
Explicit schemes of Mori-Tanaka and Kuster-Toksöz for estimating elastic properties of multiphase composites are compared and contrasted. Both methods are known to have a limited range of validity. Reexamination of the theories and comparisons to experiment lead to the conclusion that these explicit schemes should not be used to estimate properties of systems in which the host material occupies less than of the total volume. A unified approach to derivation of these explicit methods, as well as some implicit methods, is also presented.