Annotations to the Records of the Three Kingdoms

Annotations to the Records of the Three Kingdoms by Pei Songzhi (372–451) is an annotation completed in the 5th century of the 3rd century historical text Records of the Three Kingdoms, compiled by Chen Shou. After leaving his native land, Pei Songzhi became the Gentleman of Texts under the Liu Song Dynasty, and was given the assignment of editing the book, which was completed in 429. This became the official history of the Three Kingdoms period, under the title Sanguozhi zhu (zhu meaning "notes"). He went about providing detailed explanations to some of the geography and other elements mentioned in the original. More importantly, he made corrections to the work, in consultation with records he collected of the period. In regard to historical events and figures, as well as Chen Shou's opinions, he added his own commentary. From his broad research, he was able to create a history which was relatively complete, without many of the loose ends of the original. Some of the added material was colourful and of questionable authenticity, possibly fictional. All the additional material made the book close to twice the length of the original. Pei Songzhi scrupulously cited his sources, and always introduced his opinion as such.

Classics
Quoting classics was an inescapable reality of Chinese political and academic life as early as the Eastern Zhou period. Pei Songzhi often cites classics in order to contextualize quotations made by speakers in Chen Shou's original text, and occasionally to explain the philosophy or background behind a person's actions. These works do not constitute historical sources for Pei Songzhi's purposes, but are included here for sake of completeness.

Other sources
Pei Songzhi occasionally quotes other historians without citing any book or document title. Sun Sheng, Gan Bao, and Xi Zuochi are especially common. These may have been marginal notes in Pei's copy of Records of the Three Kingdoms, or personal notes to which he had access. Rarely, Pei Songzhi will report hearsay without any attribution.