The standard theory is that the latter text was produced by enlarging, expanding, and revising the former, but there is another theory that it was written first, and that the former text was produced from various sections that had been deleted from the latter.
通説では前者を増補改訂して後者が作られたと考えられているが、後者の方が先に書かれて後に様々な事情によって一部が削除したものが前者だとする説もある。