A tentative approach to entanglement measures for a system of a three-level atom interacting with a quantized cavity-fieldAbdel-Shafy F. Obada and Mahmoud Abdel-AtyEur. Phys. J. D, 27 3 (2003) 277-285DOI: https://doi.org/10.1140/epjd/e2003-00267-5