Kenneth Wai-Ting Leung Wilfred Ng Dik Lun Lee Personalized Concept-Based Clustering of Search Engine Queries. 1505-1518 2008 20 IEEE Trans. Knowl. Data Eng. 11 http://dx.doi.org/10.1109/TKDE.2008.84 db/journals/tkde/tkde20.html#LeungNL08