B. Krause, A. Hotho, and G. Stumme. 30th European Conference on IR Research, ECIR 2008, volume 4956 of Lecture Notes in Computer Science, page 101-113. Glasgow, UK, Springer, (April 2008)
M. Grahl, A. Hotho, and G. Stumme. 7th International Conference on Knowledge Management (I-KNOW '07), page 356-364. Graz, Austria, Know-Center, (September 2007)