Subluminal to superluminal pulse propagation through one-dimensional photonic crystals with a three-level atomic defect layerM. Sahrai, S. Aas and M. MahmoudiEur. Phys. J. B, 78 1 (2010) 51-58DOI: https://doi.org/10.1140/epjb/e2010-10549-2