“…The images in the database consisted of the four directions for the 16 types of banknotes ($1, $2, $5, recent $5, most recent $5, $10, recent $10, most recent $10, $20, recent $20, most recent $20, $50, recent $50, most recent $50, $100, recent $100). As shown in Table 2 , the number of images used in our study is similar to that of [ 10 ], but much larger than in most previous studies [ 11 , 12 , 13 , 14 , 15 , 16 , 17 ]. In addition, our study uses more classes than any previous study [ 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 ].…”