Sima Qian: Historical Records 13 The Genealogy of Three Dynasties
Taishigong said: The records about the Five Emperors and the Three Dynasties are very old. It is difficult to compile the history of the vassal states before the Yin Dynasty, and only the historical events since the Zhou Dynasty can be recorded. Confucius compiled the "Spring and Autumn Annals" according to the literary and historical materials, that is, he used the era number of Lu Gong and integrated the years and months of events, which was already quite detailed. However, when compiling the "Book of History", he omitted the years and months; some of them had years and months, but they were mostly missing and difficult to record. So his attitude of passing down the doubts despite doubts was very cautious!
I read the generation records, and the years were recorded from the Yellow Emperor onwards. In terms of examining the various situations of those years and the succession of the Five Virtues, the records in ancient texts are not the same, and there are even great differences. Confucius did not talk about these years and months, how could there be no reason? Therefore, I wrote the "Three Dynasties Genealogy" according to the genealogy from the Yellow Emperor to the Republican era recorded in the "Five Emperors' Genealogy" and the "Book of History".
司马迁·史记卷十三·三代世表第一
太史公曰：五帝、三代之记，尚矣。自殷以前诸侯不可得而谱，周以来乃颇可著。孔子因史文次春秋，纪元年，正时日月，盖其详哉。至于序尚书则略，无年月；或颇有，然多阙，不可录。故疑则传疑，盖其慎也。
余读谍记，黄帝以来皆有年数。稽其历谱谍终始五德之传，古文咸不同，乖异。夫子之弗论次其年月，岂虚哉！于是以五帝系谍、尚书集世纪黄帝以来讫共和为世表。