A trio of unique books have been sold by Oxfam Bookshop for more than £1,600.
The books were donated to the Cornmarket shop in Thame towards the end of 2013.
Now they have been sold and the money received will go towards providing water for half a million refugees in Syria.
A first edition J.M. Keynes book on economics was bought online for £900 by a customer from Surrey and a set of surreal art magazines – VVV – was also sold over the internet to a Japanese customer for £550.
A book written by Margaret Thatcher, including the former prime minister’s autograph, was also sold in store for £175.
Shop manager Dick Jennens said: “The signature was just what you would expect. Beautifully neat and extremely well formed.
“I saw the lady looking at the book and she went away to make a phonecall.
“When I returned from lunch, one of the volunteers said it had gone so I assume it must have been her!”
Mr Jennens admitted he first wondered if the books were worth keeping.
He even offered them to occasional customer Boris Johnson when the mayor of London visited at the start of the year.
But the rare book sales have raised valuable funds and the bookshop continues to receive unique donations.
Mr Jennens said: “A lady staggered in with a book of artwork from Venice, which is lavishly illustrated.
“We also have a series of books by Allan Mallinson at the moment, who was an army officer in the Light Dragoons.
“But we continue to provide water tanks, taps, buckets and toilets in places like Zaatari in the desert.
“There are 130,000 people in need there. That’s 10 times the size of Thame!”