Zizhi tongjian waiji 資治通鑒外紀

Zizhi tongjian waiji 資治通鑑外紀, shortly called Tongjian waiji 通鑑外紀, is a continuation to Sima Guang's 司馬光 (1019–1086) history Zizhi tongjian 資治通鑑, to be posed chronologically before the latter. The Waiji was compiled by Liu Shu 劉恕 (1032–1078, courtesy name Daoyuan 道原 or 道源), who also wrote the Shiguo jinian 十國紀年, a history of the Ten States 十國 (902~979), and some critical time-lists, the Yinianpu 疑年譜 and the Nianlüepu 年略譜.

His 10-juan long Tongjian waiji narrates the history before the year 403 BCE, the 23rd year of the reign of King Weilie 周威烈王 (r. 425–402 BCE) of the Zhou dynasty 周 (11th cent.-221 BCE), and the year in which the Zizhi tongjian begins.

The Waiji begins in the mythological age of the Three Emperors (sanhuang 三皇) and ends in the year 404. The mythological time is dealt with in one juan, that of the Xia 夏 (21th - 17th cent. BCE) and Shang 商 (17th-11th cent. BCE) dynasties in one juan, and the Zhou period in 8 juan. The book could not really be finished because Liu Shu fell ill. It was therefore in a quite raw state when it was declared finished in 1078.

The primary sources for Liu's book were abundant, and it is all the more a pity that he was never able to bring it into a good state. Liu Shu had worked with the same diligence as had been used for the compilation of the Zizhi tongjian, and used text-critical methods to solve contradictions and to emend errors. Because there is no established chronology before the year 841 BCE, the "annals" in the proper sense only begin in this year. All years before are marked as "years of doubt" (yinian 疑年). Liu Shu also added discussions about the events described in his chapters. Except the main text, there is a lengthy index of 5 juan. This index includes valuable astronomical informations that help confirming the Chinese chronology.

The Qing period 清 (1644-1911) historian Hu Kejia 胡克家 (1757–1816) wrote a commentary, Tongjian waiji zhubu 通鑑外紀注補, which was printed together with the main text. There is also a Ming period 明 (1368-1644) print (the Nanjian edition 南監本), a print from 1811 by Master Wu from Huangchuan 璜川吳氏, a print by Chen Renxi 陳仁錫, a print by the Shidun shushu Studio 石礅書塾, and that of the Shanyuan Studio 山淵堂.

The Tongjian waijian is included in the series Siku quanshu 四庫全書 and Sibu congkan 四部叢刊, as well as in the series Zizhi tongjian huike 資治通鑑彙刻 that assembles several Zizhi tongjian continuations.