M. Krötzsch, S. Rudolph, und P. Hitzler. Proceedings of the 6th International Semantic Web Conference and 2nd Asian Semantic Web Conference (ISWC/ASWC2007), Busan, South Korea, Volume 4825 von LNCS, Seite 309--322. Berlin, Heidelberg, Springer Verlag, (November 2007)