Meiyappan Nagappan Mladen A. Vouk A Model for Sharing of Confidential Provenance Information in a Query Based System. 62-69 2008 IPAW http://dx.doi.org/10.1007/978-3-540-89965-5_8 conf/ipaw/2008 db/conf/ipaw/ipaw2008.html#NagappanV08