Mahsan Rofouei Maryam Moazeni Majid Sarrafzadeh Fast GPU-based space-time correlation for activity recognition in video sequences. 33-38 2008 ESTImedia http://dx.doi.org/10.1109/ESTMED.2008.4696991 conf/estimedia/2008 db/conf/estimedia/estimedia2008.html#RofoueiMS08