Fleischhauer, M., Keitel, C. H., Narducci, L. M., Scully, M. O., Zhu, S. Y., & Zubairy, M. S. (1992). Lasing without inversion: interference of radiatively broadened resonances in dressed atomic systems. Optics Communications, 94(5), 599-608. doi:10.1016/0030-4018(92)90609-U.