What is the requirement for producing a shelf?
Example:
I have a two books within the Shelf, Book A, and Book B, and within Book A, I have Recording 1 & 2, and in Book B, I have recording 3 & 4.
After putting the recordings into their respective books, and then adding those books to the shelf, is it enough to just produce the shelf or do I have to produce the recordings first, then the books, and finally the shelf?