黄帝内经
The earliest mention of the "Huangdi Neijing" was in the bibliographical chapter of the "Hanshu" (or "Book of Han", completed in 111 CE), next to a "Huangdi Waijing" (“Outer Canon of the Yellow Emperor”) that is now lost. A scholar-physician called Huangfu Mi (215-282 CE) was the first to claim that the "Huangdi Neijing" in 18 juan (or volumes) that was listed in the "Hanshu" bibliography corresponded with two different books that circulated in his own time: the "Suwen" and the "Zhenjing" (“Needling Canon”), each in 9 juan. Since scholars believe that "Zhenjing" was one of the "Lingshu"'s earlier titles, they agree that the Han dynasty "Huangdi Neijing" was made of two different texts that are close in content to the works we know today as the "Suwen" and the "Lingshu".