V. Malaise, L. Hollink, and L. Gazendam. Proceedings of the Workshop on Semantic Search (SemSearch 2008) at the 5th European Semantic Web Conference (ESWC 2008) Tenerife, Spain, June 2nd, 2008, page 44--58. (2008)
X. Wang, L. Zhang, F. Jing, and W. Ma. Proceedings of the 15th International Conference on World Wide Web, page 1045-1046. Edinburgh, Scotland, ACM Press, (May 2006)