Arjun Dasgupta Nan Zhang Gautam Das Surajit Chaudhuri Privacy preservation of aggregates in hidden databases: why and how? 153-164 2009 SIGMOD Conference http://doi.acm.org/10.1145/1559845.1559863 conf/sigmod/2009 db/conf/sigmod/sigmod2009.html#DasguptaZDC09