M. Koolen, G. Kazai, and N. Craswell. WSDM '09: Proceedings of the Second ACM International Conference on Web Search and Data Mining, page 44--53. New York, NY, USA, ACM, (2009)
K. Nakayama, T. Hara, and S. Nishio. Proceedings of the Workshop on Semantic Search (SemSearch 2008) at the 5th European Semantic Web Conference (ESWC 2008) , June 2, 2008, Tenerife, Spain, volume 334 of CEUR Workshop Proceedings, CEUR-WS.org, (2008)