The 16th Century books were discovered in a salt mine store
A former US soldier has returned two historic books he took as "souvenirs" during World War II.
Robert Thomas handed over the two books, both 400 years old, to the German ambassador during a ceremony at the US national archives in Washington.
The texts were taken from a salt mine in western Germany, where they were being kept safe during allied bombing.
The 83-year-old former soldier said they were in a similar condition to when he had discovered them.
"I kept them in two boxes in the darkest and coolest place at my house," Mr Thomas said.
He described, as a young soldier in Germany, coming across a chamber "filled with thousands of books, from floor to the ceiling".
Like many valuable artefacts, the books were kept in an underground mine at Merkers, near Frankfurt.
The German ambassador, Klaus Scharioth, said the books would be returned to the libraries which had owned them before the war - the University of Bonn and the Diocesan Museum of Paderborn.
"It's such a 'Gluecksfall' for Germany that we have these books back," he said, referring to the German term for a stroke of luck.
Mr Scharioth said the return of the ancient texts represented a "sign of friendship and trust".