Yannis Petrakis Georgia Koloniari Evaggelia Pitoura On Using Histograms as Routing Indexes in Peer-to-Peer Systems. 16-30 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=3367&spage=16 2004 conf/dbisp2p/2004 DBISP2P db/conf/dbisp2p/dbisp2p2004.html#PetrakisKP04