If the poem that you see in your Documents mentions the copper/bronze door, then that's fine - the information has been extracted from the book for you.
If the clue has you truly stumped, here is the answer:
Enter that into the card catalogue for your new clue to continue with the game.
I think that should work without having to examine the Babylonian door in close-up, but if not, then that's all you have to do.
