A. Hotho, R. Jäschke, C. Schmitz, and G. Stumme. Proc. First International Conference on Semantics And Digital Media Technology (SAMT), volume 4306 of LNCS, page 56-70. Heidelberg, Springer, (December 2006)
S. Niwa, T. Doi, and S. Honiden. ITNG '06: Proceedings of the Third International Conference on Information Technology: New Generations (ITNG'06), page 388--393. Washington, DC, USA, IEEE Computer Society, (2006)