P. Teufl, and G. Lackner. 10th International Conference on Knowledge Management and Knowledge Technologies 1–3 September 2010, Messe Congress Graz, Austria, page 18 - 18. (2010)
G. Grimnes, P. Edwards, and A. Preece. Proceedings of the 5th European Semantic Web Conference (ESWC 2008), volume 5021 of Lecture Notes in Computer Science, page 303-317. Springer, (2008)
G. Gottlob, G. Orsi, and A. Pieris. (2011)cite arxiv:1112.0343Comment: Extended version of "Ontological Queries: Rewriting and Optimization" presented at ICDE 2011.