M. Carman, M. Baillie, and F. Crestani. SSM '08: Proceeding of the 2008 ACM workshop on Search in social media, page 27--34. New York, NY, USA, ACM, (2008)
P. Heymann, G. Koutrika, and H. Garcia-Molina. WSDM '08: Proceedings of the International Conference on Web Search and Web Data Mining, page 195--206. New York, NY, USA, ACM, (February 2008)