Eduardo Sany Laber Renato Carmo Yoshiharu Kohayakawa Querying Priced Information in Databases: The Conjunctive Case. 6-15 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=2976&spage=6 2004 conf/latin/2004 LATIN db/conf/latin/latin2004.html#LaberCK04