E. Ferrara, O. Varol, F. Menczer, and A. Flammini. Proceedings of the first ACM Conference on Online Social Networks, page 213--222. New York, NY, USA, ACM, (2013)
B. Krause, R. Jäschke, A. Hotho, and G. Stumme. HT '08: Proceedings of the Nineteenth ACM Conference on Hypertext and Hypermedia, page 157--166. New York, NY, USA, ACM, (2008)