Dispersive and absorptive properties of a Λ-type atomic system with two fold lower-levels M. Sahrai, R. Etemadpour and M. Mahmoudi Eur. Phys. J. D, 59 3 (2010) 463-471 Published online: 29 June 2010 DOI: 10.1140/epjd/e2010-00172-x