Hartman effect in one-dimensional photonic crystals with a three-level atomic defect layer M. Sahrai, S. Aas, M. Aas and M. Mahmoudi Eur. Phys. J. B, 83 3 (2011) 337-342 Published online: 12 October 2011 DOI: 10.1140/epjb/e2011-20224-9