1. Croft, W.B., Turtle, H.R., Lewis, D.D.: The use of phrases and structured queries in information retrieval. In Bookstein, A., Chiaramella, Y., Salton, G., Raghavan, V.V., eds.: Proc. of the 4th Annual Intern. Conf. on Research and Development in IR, ACM-SIGIR, Chicago, Illinois (1991) 32–45
2. Grefenstette, G., ed.: Cross-Language Information Retrieval. Kluwer Academic, Boston (1998)
3. Woods, W. A.: Conceptual indexing: A better way to organize knowledge. Technical Report TR-97-61, Sun Microsystems Laboratories (1997)
4. Woods, W. A.: Conceptual indexing: Practical large-scale ai for efficient information access. In: Proc. of the 17th National Conf. on Artificial Intelligence and 12th Conf. on Innovative Applications of Artificial Intelligence, AAAI Press / The MIT Press (2000) 1180–1185
5. Khan, L., McLeod, D., Hovy, E. H.: Retrieval effectiveness of an ontology-based model for information selection. Int. Journal on Very Large Data Bases 13 (2004) 71–85