Xu , Ting-TingXiong , Wei and Ye , Liu. (2013). A Scheme for Eneration of Multi-Photon GHZ States with Cross-Kerr Nonlinearities.
            <i>Journal of Atomic and Molecular Sciences</i>. <i>4</i> (1).
            72-78.
         doi:10.4208/jams.030111.032211a