Before revision:  ~\mbox{%DIFAUXCMD \cite{bcg-ffq-13}\hspace{0pt}%DIFAUXCMD } [ [ \eps\eps .
After revision:  ~\mbox{%DIFAUXCMD \cite{bcg-ffq-13}\hspace{0pt}%DIFAUXCMD } [ [ . Given \theta>0, and n time-stamped points spread over m regions in a map, for any query window W, we propose a data structure of size O(n/\eps\eps .