Tieyun Qian Qing Li Bing Liu 0001 Hui Xiong Jaideep Srivastava Phillip C.-Y. Sheu What's behind topic formation and development: a perspective of community core groups. 1843-1846 2009 CIKM http://doi.acm.org/10.1145/1645953.1646245 conf/cikm/2009 db/conf/cikm/cikm2009.html#QianLLXSS09