The Rough Guide to Shabadabadon

 was a book that the Fifth Doctor took with him on the way to the famous ice caves of Shabadabadon. He discarded it when he instead landed in the Gogglebox in the far future. (AUDIO: The Gathering) During his sixth incarnation, he returned to Shabadabadon to retrieve the book but was unable to locate it. (AUDIO: The Reaping)