Partial Resonances of Three-Phase Composites at Long Wavelengths
  We investigate the behaviour of a three-phase composite, structured as a hexagonal array of coated cylinders, when the sum of the dielectric constants of the core and shell equals zero. In such cases, the absorption of the composite is the same as the absorption of a periodic array of solid cylinders of core material and radius equal to the outer radius of the original coated cylinder. When the sum of the dielectric constants of the shell and matrix equals zero, the composite has the same absorption as a periodic array of solid cylinders of core material, and radius exceeding the shell radius. 
N. A. Nicorovici, R. C. McPhedran, G. W. Milton and L. C. Botten