Shizhu Liu Yuval Merhav Wai Gen Yee Nazli Goharian Ophir Frieder A sentence level probabilistic model for evolutionary theme pattern mining from news corpora. 1742-1747 2009 SAC http://doi.acm.org/10.1145/1529282.1529672 conf/sac/2009 db/conf/sac/sac2009.html#LiuMYGF09