Akira Utsumi Nobuji Tetsutani Human Tracking using Multiple-Camera-Based Head Appearance Modeling. 657-662 2004 conf/fgr/2004 FGR http://csdl.computer.org/comp/proceedings/fgr/2004/2122/00/21220657abs.htm db/conf/fgr/fgr2004.html#UtsumiT04