Keitel, Christoph H. Division Prof. Dr. Christoph H. Keitel, MPI for Nuclear Physics, Max Planck Society;
http://www.sciencedirect.com/science/article/pii/003040189290426R (Publisher version)
Manka, A. S., Keitel, C. H., Zhu, S. Y., Fleischhauer, M., Narducci, L. M., & Scully, M. O. (1992). Quantum theory of laser emission from driven three-level atoms. Optics Communications, 94(1-3), 174-182. doi:10.1016/0030-4018(92)90426-R.