Guannan Gong Liang Hu Kuo Zhao Jinxin He Yuefeng Xu Ying Duan SPS-VN: Research on the Security Policy System for Virtual Network. 44-47 2006 conf/csreaSAM/2006 Security and Management db/conf/csreaSAM/csreaSAM2006.html#GongHZHXD06