2Salton G, McGill M J. Introduction to Modem Information Retrieval.McGraw-Hill, 1983.
3Robertson S, Sparck-Jones K. Relevance Weighting of Search Terms.Journal of American Society for Information Science, 1976, 3(27):129-146.
4Deerwester S, Dumais S T, Furnas G W, et al. Indexing by Latent Semantic Analysis. Journal of the American Society for Information Science, 1990, 41(6): 391-407.
5Massot M, Rodriguez H, Ferres D. QA UdG-UPC System at TREC-12.In: Proceedings of the Twelfth Text Retrieval Conference, 2003:762.
