greatly praising the work. The work became popular and a key source of information on rites, music, criminal law, and governance for the people of the time, and it was said that it was so detailed that the information from the last thousand years could be accessible easily. Background Du You was born in 735, during the reign of Emperor Xuanzong. His family, the Du clan of Jingzhao, was from the Tang Dynasty capital Chang'an and traced its ancestry to a line of officials of Chu, Qin Dynasty, Han Dynasty, Cao Wei, Jin Dynasty (266–420), Northern Zhou, and Tang. Du You's great-grandfather Du Xingmin (), grandfather Du Que (), and father Du Xiwang () all served as officials in Tang governments. Du You's own civil service career started from a position that he was given on account of his heritage — the military advisor to the governor of Ji'nan Commandery (濟南, in modern Jinan, Shandong). He later was made secretary general of Yan County (剡縣, in modern Shaoxing, Zhejiang). As he went through Run Prefecture (潤州, in modern Zhenjiang, Jiangsu), he went to see the prefect, Wei Yuanfu (), who had previously been a beneficiary of Du Xiwang's, but initially, Wei, not remembering that, treated him only like the son of an old friend. On one way during Du You's visit, however, when Wei was judging over a difficult case, Wei wanted to test Du and therefore asked him for his opinions, and his opinions were all correct ones, impressing Wei. Wei kept him as legal advisor. Later, when Wei served successively as the governor of Zhexi Circuit (浙西, headquartered in modern Zhenjiang) and military governor (Jiedushi) of Huainan Circuit (淮南, headquartered in modern Yangzhou, Jiangsu), he continued to invite Du to serve on staff and entrusted Du with many responsibilities. Later, Du was recalled to Chang'an to serve as Gongbu Langzhong (), a supervisorial official at the ministry of public works (工部, Gongbu). Yet later he successively served as the director of the Qingmiao () tax (i.e., taxation on young food crops) for Jiangxi Circuit (江西, headquartered in modern Nanchang, Jiangxi); the prefect of Fu Prefecture (撫州, in modern Fuzhou, Jiangxi); and the director of Rong District (容管, headquartered in modern Yulin, Guangxi). During Emperor Dezong's reign During the reign of Emperor Xuanzong's great-grandson Emperor Dezong, after Yang Yan became chancellor in 779, Yang had Du recalled to Chang'an,