Baik Hoh Marco Gruteser Ryan Herring Jeff Ban Daniel B. Work Juan Carlos Herrera Alexandre M. Bayen Murali Annavaram Quinn Jacobson Virtual trip lines for distributed privacy-preserving traffic monitoring. 15-28 2008 MobiSys http://doi.acm.org/10.1145/1378600.1378604 conf/mobisys/2008 db/conf/mobisys/mobisys2008.html#HohGHBWHBAJ08