Devi Parikh C. Lawrence Zitnick 1425-1432 2011 CVPR https://doi.org/10.1109/CVPR.2011.5995450 https://doi.ieeecomputersociety.org/10.1109/CVPR.2011.5995450 conf/cvpr/2011 db/conf/cvpr/cvpr2011.html#ParikhZ11