1. Agarwal, A. (2006). Search Engine Index Sizes: Google vs Yahoo vs MSN. Digital Inspiration. Retrieved August 2, 2006 from http://labnol.blogspot.com/2006/07/search-engine-index-sizes-google-vs.html.
2. Al-Khalifa, H. S., & Davis, H. C. (2006). Folksonomies versus automatic keyword extraction: An empirical study. In Proceedings of IADIS Web Applications and Research 2006 (WAR2006). Retrieved January 20, 2007, from http://eprints.ecs.soton.ac.uk/12547/.
3. A subjective measure of Web search quality;Beg;Information Sciences,2005
4. Relevance for browsing, relevance for searching;Bodoff;Journal of the American Society for Information Science and Technology,2006
5. Automatic performance evaluation of Web search engines;Can;Information Processing and Management,2004