L. Leonardi Salvatore Orlando Alessandra Raffaetà Alessandro Roncato Claudio Silvestri Frequent spatio-temporal patterns in trajectory data warehouses. 1433-1440 2009 SAC http://doi.acm.org/10.1145/1529282.1529603 conf/sac/2009 db/conf/sac/sac2009.html#LeonardiORRS09