R. Wetzker, C. Zimmermann, C. Bauckhage, and S. Albayrak. Proceedings of the third ACM international conference on Web search and data mining, page 71--80. New York, NY, USA, ACM, (2010)
W. Feng, and J. Wang. Proceedings of the 18th ACM SIGKDD international conference on Knowledge discovery and data mining, page 1276--1284. New York, NY, USA, ACM, (2012)