Wolfgang Nejdl Wolf Siberski Uwe Thaden Wolf-Tilo Balke Top-k Query Evaluation for Schema-Based Peer-to-Peer Networks. 137-151 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=3298&spage=137 2004 conf/semweb/2004 International Semantic Web Conference db/conf/semweb/iswc2004.html#NejdlSTB04