B. Bullock, H. Lerch, A. Roßnagel, A. Hotho, and G. Stumme. Proceedings of the 11th International Conference on Knowledge Management and Knowledge Technologies, page 15:1--15:8. New York, NY, USA, ACM, (2011)
L. Backstrom, and J. Leskovec. Proceedings of the fourth ACM international conference on Web search and data mining, page 635--644. New York, NY, USA, ACM, (2011)