I borrowed a book, "Practical English Usage", by Michael Swan, published by Oxford University Press.
There is a NLF green mark on the bottom-right corner of the book cover, on the title page sticks a notice:
No Late Collection
This book is part of our No Late Fee Collection. We will renew it automatically for up to six months so there will be no late fees. Please return the book within six months or, if you want to keep it longer, please renew it.
This policy seems very considerate. To my experience, all reference books or dictionaries are not allowed to be taken out of the library, they are used to be "REFERENCED" inside the reading room, then these books are just decorations, standing on the book shelves for collecting dust.