Controllable shape-matched propagation of two signal beams in a double-Λ atomic ensemble Zhuan Li, Li-Ping Deng, Li-Sen Xu and Kaige Wang Eur. Phys. J. D, 40 1 (2006) 147-156 Published online: 21 June 2006 DOI: 10.1140/epjd/e2006-00141-0