F. Abel, N. Henze, and D. Krause. CIKM '08: Proceeding of the 17th ACM conference on Information and knowledge mining, page 1429--1430. New York, NY, USA, ACM, (2008)
A. Hotho, R. Jäschke, C. Schmitz, and G. Stumme. Proc. First International Conference on Semantics And Digital Media Technology (SAMT), volume 4306 of LNCS, page 56-70. Heidelberg, Springer, (December 2006)