H. Williams and J. Zobel. Compressing integers for fast file access. Computer Journal, 42(3): 193-201, 1999. H. Williams, J. Zobel, and P. Anderson. What's next? In-dex structures for efficient phrase querying. In Proc. Aus-tralasian Database Conference, pages 141-1 52, Auckland, New Zealand, January 1999. Springer. I. Witten, A. Moffat, and T. Bell. Managing Gigabytes: Compressing and Indexing Documents and Images. Morgan Kaufmann Publishers, Los Altos, CA 94022, USA, second edition, 1999. Y. Yang and X. Liu. A re-examination of text categorization methods. In Proc. ACM-SIGIR International Conference on Research and Development in Information Retrieval, pages 42-49, Berkeley, California, August 1999. ACM Press. Y. Yang and J. Pedersen. A comparative study on feature se-lection in text categorization. In Proc. International Confer-ence on Machine Learning, pages 412-420, Nashville, July 1997. Morgan Kaufmann. Y. Yang and J. Wilbur. Using corpus statistics to remove redundant words in text categorization. JoumaI of the Amer-ican Society for Information Science, 47(5):357-369, 1996. J. Zobel, H. Williams, and S. Kimberley. Trends in retrieval system performance. In Proc. Australasian Computer Sci-ence Conference, volume 22, pages 241-248, Canberra, Jan-uarymebruary 2000. IEEE Computer Society Press.