P. Heymann, und H. Garcia-Molina. Second ACM International Conference on Web Search and Data Mining (WSDM 2009), Late Breaking Results Session, Seite 1--4. Stanford InfoLab, (Februar 2009)
M. Carman, M. Baillie, R. Gwadera, und F. Crestani. Proceedings of the 32nd international ACM SIGIR conference on Research and development in information retrieval, Seite 123--130. New York, NY, USA, ACM, (2009)