Xuan Tian Xiaoyong Du He Hu Haihua Li Modeling User_s Cognitive Structure in Contextual Information Retrieval. 349-353 2007 FSKD (4) http://dx.doi.org/10.1109/FSKD.2007.410 conf/fskd/2007-4 db/conf/fskd/fskd2007-4.html#TianDHL07