Historical Records Biography of Hengshan Mountain in Huainan: "So Wang Nai ordered officials and slaves to enter the palace as the imperial seal." "Biography of Cao Wangming in the New Tang Dynasty": "At the beginning of Wuhou, the strong were put to death, and the young were not official slaves or not seen by the world." Song Chen Shidao's "Autumn Huai" No.6: "Officials and slaves are covered with blue silk, and the house is broken." Guo Moruo's Historical Draft of China, Part III, Chapter 1, Section 2: "There is a set of management organization in the government-run handicraft institutions. The direct producers are government slaves, criminals and migrant workers, and some are employees, that is,' servants'. "