In the period of the North and South Song Dynasties, a good number of scholars paid attention to historical investigation. Sima Guang exhaustively investigated differences of historical events recorded in different works and explained the reasons of selection and deletion in writing An Investigation of Differences in General Chronicles. Other such examples included Casual Notes in Rongzhai by Hong Mai, and Notes of Bewildering Points by Wang Yinglin, which not only enriched the contents but diversified the forms and extended the depths and expanse of historical investigation. Owing to Sima Guang's initiation and Hong Mai and Wang Yinglin’s advocating as well as the proper soil offered by the times, historical investigation gained as great advance in the Song Dynasties and opened a new path for further development of traditional academic studies.

the history of historical study in the Song Dynasty; historical research; An Investigation of Differences in General Chronicles; Casual Notes in Rongzhai; Notes of Bewildering Points