During the middle era of the Heian period and later, government officials compiled various chronicles, including "Ruiju Kokushi" (classified national history), "Nihongi Ryaku" (a summary of Japanese chronologies), and "Hyakuren sho" (history book from the Kamakura period), as the historical documents that they would refer to in conducting their political operations.
平安中期以降は官人らが政務処理に先例を参照するための歴史資料として『類聚国史』『日本紀略』『百錬抄』やその他各種の年代記が編纂された。