“…For example, on the IITD DB, some methods [30, 32, 35, 36, 38, 47] work on 230 subjects, others [4, 34, 46, 48] work on 235 subjects while [15] works on 215 subjects. Some methods [4, 15, 35, 38, 48] considered the original number of images per subject while others [30, 32, 36, 46, 47] fix this number to five. Some methods [15, 34, 35, 38, 47, 48] considered a training set with a different number of images while others [4, 30, 32, 36, 46] do not.…”