Xiangdong Zhou Mei Wang Qi Zhang Junqi Zhang Baile Shi Automatic image annotation by an iterative approach: incorporating keyword correlations and region matching. 25-32 2007 conf/civr/2007 CIVR http://doi.acm.org/10.1145/1282280.1282284 db/conf/civr/civr2007.html#ZhouWZZS07