A previously unknown piece of music by Mozart has been discovered at a library in western France.
Ulrich Leisinger, head of research at the International Mozarteum Foundation in Austria, said the composer's handwriting was clearly identifiable, and he had no doubt it was an original piece handwritten by Mozart.
The sheet was found among the archives by staff at a library in Nantes.
Mr Leisinger said the municipal Mediatheque library contacted his foundation to ask for help authenticating the work.
The score was written on a sheet of paper just 10cm in size. It appears to be a "Credo in D major".
It was part of the collection of Pierre-Antoine Laboucheroe, a 19th-century collector who donated his legacy to the city.
The score was catalogued as part of the library's collection, but was later "entirely forgotten" about.
It was rediscovered by the library as it re-catalogued its archives, and authenticated by a researcher from the Mozarteum Foundation last year.
Mr Leisinger said there had been just 10 Mozart finds of such importance over the past 50 years.
If sold, the single sheet would likely fetch around $US100,000.