S. McNee, N. Kapoor, and J. Konstan. Proceedings of the 2006 20th anniversary conference on Computer supported cooperative work, page 171--180. New York, NY, USA, ACM, (2006)
R. Wetzker, W. Umbrath, and A. Said. Proceedings of the WSDM '09 Workshop on Exploiting Semantic Annotations in Information Retrieval, page 25--29. New York, NY, USA, ACM, (2009)
S. Doerfel, R. Jäschke, A. Hotho, and G. Stumme. Proceedings of the 4th ACM RecSys workshop on Recommender systems and the social web, page 9--16. New York, NY, USA, ACM, (2012)