1. Baeza-Yates, R. and Ribeiro-Neto, B. 1999.Modern Information Retrieval38–41.
2. Bender, E. A. 1996.Mathematical Methods in Artificial Intelligence, 38–41. IEEE Computer Society Press.
3. Knowledge-based document retrieval in office environments
4. Chen, H. 2001.Knowledge Management Systems-A Text Mining Perspective, 24–25. University of Arizona.