Zdenek Kalal Krystian Mikolajczyk Jiri Matas Forward-Backward Error: Automatic Detection of Tracking Failures. 2756-2759 2010 ICPR http://dx.doi.org/10.1109/ICPR.2010.675 conf/icpr/2010 db/conf/icpr/icpr2010.html#KalalMM10