S. Bao, G. Xue, X. Wu, Y. Yu, B. Fei, und Z. Su. WWW '07: Proceedings of the 16th international conference on World Wide Web, New York, NY, USA, ACM Press, (2007)
M. Burghardt, M. Heckner, und C. Wolff. Volume 4 von Library and Information Science, Kapitel 2, Seite 19--46. Emerald Group Publishing Limited, (2012)
D. Donato, F. Bonchi, T. Chi, und Y. Maarek. Proceedings of the 19th international conference on World wide web, Seite 321--330. New York, NY, USA, ACM, (2010)