Fluorescence from doubly driven four-level atoms - A density matrix approachA. Narayanan, R. Srinivasan, U. K. Khan, A. Vudayagiri and H. RamachandranEur. Phys. J. D, 31 1 (2004) 107-112DOI: https://doi.org/10.1140/epjd/e2004-00123-2