The Zhenguan shizu zhi 貞觀氏族志 "Record of eminent families from the Zhenguan reign (627-649)" is a collection of family registers from the early Tang period 唐 (618-907). In 100 juan "scrolls", the book lists the most eminent families of the empire. The book reflects the power of a very small number of mighty families which had dominated eastern China during the 5th and 6th centuries, such as the Cui 崔, Lu 盧, Wang 王 or Xie 謝. Emperor Taizong 唐太宗 (r. 626-649) wanted to curtail the power of these clans and wanted to express this in a kind of jurisdictional book in which each family was attributed one of nine specific meritorious ranks. He thus ordered some of his highest officials, like Gao Shilian 高士廉, Wei Ting 韋挺, Cen Wenben 岑文本 and Linghu Defen 令狐德芬, to compile a new family register of the empire. When the draft was submitted Taizong was not content that there were still some eastern families graded with the first rank. In 638 a new version was submitted which included 293 families with 1,651 households. Cui Mingan 崔民幹, for example, whose family had occupied the first rank in the first version, was now graded on the third rank. By this measure members of his family would not any more able to obtain a state office of the first official rank. Inspite of this formal change the Zhenguan shizu zhi could not block the way to influential positions. Nevertheless the book initiated a replacement of the traditional gentry families of the Southern and Northern Dynasties period 南北朝 (300~600) by the followers of the Li 李 family, the founders of the Tang dynasty.
Source: Hu Rulei 胡如雷 (1992). "Zhenguan shizu zhi 貞觀氏族志", in: Zhongguo da baike quanshu 中國大百科全書, Zhongguo lishi 中國歷史, vol. 3, p. 1519. Beijing/Shanghai: Zhongguo da baike quanshu chubanshe.