X. Jia, S. Ying, H. Cao, and D. Xie. Sixth International Conference on Grid and Cooperative Computing, 2007. GCC 2007, page 96--103. IEEE, (August 2007)
A. Boukottaya, C. Vanoirbeek, F. Paganelli, and O. Khaled. Conceptual Modelling 2004, First Asia-Pacific Conference on Conceptual Modelling (APCCM2004), Dunedin, New Zealand, January 18-22, 2004, volume 31 of CRPIT, page 81--90. Australian Computer Society, (2004)