Behemot listed above these quoted writings are treated with utmost respect and authority ("as it is written..." "The scripture says", etc.)
Cyrus,
A lot of guessing is involved in where such sources may have originated. Take 1 Cor 2:9 for example. "Gill stated: Ver. 9. But as it is written, &c.] Not in an apocryphal book, called the Apocalypse of Elijah the prophet, as some have thought, but in #Isa 64:4 with some variation; and is brought to prove that the Gospel is mysterious and hidden wisdom, unknown to the princes of this world, and ordained before the world was, for the glory of the saints:" And since we are now in another language the translation of such texts is another factor that causes such variations. Often it is the message and not exact wording that matters. That is why the Gospel writers did not quote our Lord exactly but often interpreted his words instead to suit their audience. Compare Matt, Mark and Luke regarding the sign to see this. Also the word Heavens and God interchange. I took the time to check the verses and we do not find "it is written" in them or proof of use. This comparison list is simply an assumption and yet what difference does it make if someone else said something similar? I found other answers for such texts and words that were ignored here in my Bible references and you can as well. Just as I said earlier even the use of their writings does not validate their entire work. After all such works were common to them all.
Joseph