Bounds for effective dielectric permittivity in differential medium   approximation
  Theoretical approach is proposed to description of dielectric properties of matrix disperse systems which consists of dielectric matrix with embedded in metallic inclusions. On the basis of effective differential medium approximation the analytical expressions are obtained for the effective dielectric permittivity of the matrix disperse system with inclusions of spherical and ellipsoidal shape. The analysis of limits of possible values of the real and imaginary parts of is carried out depending on system parameters. 
Vitaliy N. Pustovit