Generally speaking, {HEAD ~ photonic band gap materials} have {TAIL ~ the property} of preventing electromagnetic radiation having some discrete wavelength or range of wavelengths from propagating along a given direction in a material 
have
Generally speaking , { HEAD ~ photonic band gap materials } have { TAIL ~ the property } of preventing electromagnetic radiation having some discrete wavelength or range of wavelengths from propagating along a given direction in a material
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH