1. Antoniou, G., & van Harmelen, F. (2004). Web Ontology Language: OWL. In S. Staab & R. Studer (Eds.), Handbook On Ontologies. Karlsruhe: Springer.
2. Beer, T., Höpken, W. R., Zanker, M., Rasinger, J., Jessenitschnig, M., Fuchs, M., & Werthner, H. (2006). An Intelligent Information Push Service for the Tourist Domain. Paper presented at the European Conference on Artificial Intelligence (Workshop on Recommender Systems), Riva del Garda.
3. Beierle, C, & Kern-Isberner, G. (2003). Methoden wissensbasierter Systeme. Hagen: Vieweg.
4. Bieger, T. (2005). Management von Destinationen, 6. Auflage. München, Wien: Oldenbourg
5. Brachman, R. J., & Levesque, H. J. (2004). Knowledge Representation and Reasoning. San Francisco: Morgan Kaufmann.