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One of the books contains a sketch of the British naturalist's famous Tree of Life.
Two of Charles Darwin's notebooks have been found 22 years after going missing.
They were discovered in a gift bag that was left on the floor of Cambridge University's library in England last month, along with a typed note saying "Librarian Happy Easter."
One of the books contains a sketch of the British naturalist's famous Tree of Life.
An investigation is ongoing.