Dongfeng Chen Rada Chirkova Maxim Kormilitsin Fereidoon Sadri Timo J. Salo Query optimization in xml-based information integration. 1405-1406 2008 CIKM http://doi.acm.org/10.1145/1458082.1458303 conf/cikm/2008 db/conf/cikm/cikm2008.html#ChenCKSS08