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)
Y. Yanbe, A. Jatowt, S. Nakamura, and K. Tanaka. JCDL '07: Proceedings of the 2007 conference on Digital libraries, page 107--116. New York, NY, USA, ACM Press, (2007)