The UNESCO programme Memory of the World aims to protect and facilitate access to the world's documentary heritage. Examples of pilot projects include the production of a CD-ROM of the Radzivill Chronicle, a 15th century illuminated manuscript relating the history of Russia from the 5th to the 13th centuries; and the setting up of a national committee in Yemen to select for preservation the most precious manuscripts found in the ceiling of the Great Mosque of Sana'a. UNESCO is also involved in efforts to preserve the world's film stock, the fragile nature of which means that many great works of this art which distinguishes the twentieth century may soon be lost.