Shoku Nihongi
The Fujiwara no Hirotsugu Rebellion is sparsely documented and most of what is known about it, including exact dates, derives from a single historical source, the "Shoku Nihongi". Completed in 797, this is one of the imperially commissioned Six National Histories and covers the time from 697 to 791. It is a valuable document for historians, though not all dates in it should be considered exact.