Paolo Atzeni Wesley W. Chu Hongjun Lu Shuigeng Zhou Tok Wang Ling Conceptual Modeling - ER 2004, 23rd International Conference on Conceptual Modeling, Shanghai, China, November 2004, Proceedings ER Lecture Notes in Computer Science 3288 Springer 2004 3-540-23723-2 db/conf/er/er2004.html