M. Freiberg. 457. University of Würzburg, Institute of Computer Science, Department of Artificial Intelligence and Applied Informatics, Am Hubland, D-97074 Würzburg, Germany, (March 2009)
C. Paris, N. Colineau, and R. Wilkinson. HT '09: Proceedings of the Twentieth ACM Conference on Hypertext and Hypermedia, New York, NY, USA, ACM, (July 2009)