What is the word for turn these in a book?

The word "turn these in" in a book could have a few different meanings depending on the context. Could you please give me more information about what you're referring to?

For example, are you talking about:

* Submitting assignments: If you are a student, "turn these in" might refer to submitting homework, essays, or other assignments to your teacher.

* Returning borrowed items: If you are a librarian, "turn these in" might refer to returning borrowed books or other materials.

* A specific instruction: "Turn these in" could be a direct instruction given within the book itself, perhaps as part of an interactive exercise or puzzle.

Knowing the context will help me understand what you're looking for!