Daniele Riboni Linda Pareschi Claudio Bettini Sushil Jajodia Preserving Anonymity of Recurrent Location-Based Queries. 62-69 2009 TIME http://doi.ieeecomputersociety.org/10.1109/TIME.2009.8 conf/time/2009 db/conf/time/time2009.html#RiboniPBJ09