The back of the title page. CIP nuclear font size is an important index to test whether books published since 1990s are genuine. Before 2000, it was 9 digits. In 2000, 9 digits coexisted with 10 digits. After 2000, it was 10 digits, which was printed on the back of the title page of the book. As the sole producer of CIP data, the Information Center of the General Administration of Press and Publication is responsible for the production of CIP data, and no unit may produce it by itself, thus ensuring the uniqueness and authority of the data.