Local constitutive parameters of metamaterials
  The reason of the non-locality of constitutive (material) parameters extracted in a usual way from the reflection-transmission coefficients of composite slab at moderately low frequencies is explained. The physical meaning of these parameters is clarified. Local constitutive parameters of metamaterial lattices are discussed and their existence at moderate frequencies is demonstrated. It is shown how to extract local material parameters from the dispersion characteristics of an infinite lattice and from reflection and transmission coefficients of metamaterial layers. 
Constantin R. Simovski