K. Winkler, and M. Spiliopoulou. Proceedings of the K-CAP 2001 Workshop on Knowledge Markup and Semantic Annotation, page 59--68. Victoria, BC, Canada, (October 2001)
G. Weikum. Invited Talk at the 8th German Database Conference / Datenbanksysteme in Büro, Technik und Wissenschaft (BTW), Freiburg, Germany, (March 1999)