1. Baeza-Yates, R., Ribeiro-Neto, B.: Modern information retrieval, pp. 117–134. Addison-Wesley, Reading (1999)
2. Bookman, L., Woods, W.: Linguistic Knowledge Can Improve Information Retrieval. In: Proceedings of ANLP-2000, Seattle, WA, May 1-3, pp. 1–9 (2000)
3. Chang, C., Hsu, C.: Integrating query expansion and conceptual relevance feedback for personalized web information retrieval. Computer Networks and ISDN Systems 30(1-7), 621–623 (1998)
4. Chang, Y., Choi, I., Choi, J., Kim, K., Raghavan, V.V.: Conceptual Retrieval Based on Feature Clustering of Documents. In: Workshop on Mathematical/Formal Methods in Informa- tion Retrieval at the 25th Annual International ACM SIGIR Conference on Research and Development in IR, in Tampere, Finland, August 15, pp. 89–104 (2002)
5. Cormen, T.H., Leiserson, C.E., Rivest, R.L., Stein, C.: Introduction to algorithm, 2nd edn., pp. 498–501. MIT Press, Cambridge (2001)