Rui Zhou 0001 Chengfei Liu Junhu Wang Jianxin Li Containment between Unions of XPath Queries. 405-420 2009 DASFAA http://dx.doi.org/10.1007/978-3-642-00887-0_36 conf/dasfaa/2009 db/conf/dasfaa/dasfaa2009.html#ZhouLWL09