Paola Bonizzoni Gianluca Della Vedova Riccardo Dondi The <i>k</i>-Anonymity Problem Is Hard. 26-37 2009 FCT http://dx.doi.org/10.1007/978-3-642-03409-1_4 conf/fct/2009 db/conf/fct/fct2009.html#BonizzoniVD09