Paul A. Viola Michael J. Jones Daniel Snow Detecting Pedestrians Using Patterns of Motion and Appearance. 734-741 2003 conf/iccv/2003 ICCV http://csdl.computer.org/comp/proceedings/iccv/2003/1950/02/195020734abs.htm db/conf/iccv/iccv2003-2.html#ViolaJS03