Book of Sui
The format used in the text follows the composite historical biography format (斷代紀傳體) established by Ban Gu in the Book of the Later Han with three sections: annals (紀), treatises (志), and biographies (傳). The extensive set of 30 treatises, sometimes translated as "monographs", in the Book of Sui was completed by a separate set of authors and added in 656 – 20 years after the original text was completed. The treatises cover the Liang, Chen, Northern Qi, and Northern Zhou dynasties in addition to the Sui. In addition to the Book of Liang and Book of Chen, the Book of Sui is an essential source of information on the subjects covered for those dynasties. The treatises on classics (經籍) are especially important because the Book of Sui is the only standard history including such a section since the Book of Han and contains essential bibliographical information for the period from the Later Han (25–220) to the Sui dynasty. The treatises were initially circulated as a separate set titled "Treatises of the History of the Five Dynasties" (五代史志).