S. Auer, C. Bizer, G. Kobilarov, J. Lehmann, R. Cyganiak, and Z. Ives. The Semantic Web: Proceeding of the International Semantic Web Conference 2007 and the Asian Semantic Web Conference 2007 (ISWC2007+ASWC2007), page 722--735. Busan, Korea, Springer, (November 2007)