Madrid, 10 September 1981 - Internal museum documents Certificate for the reception of Guernica, and its stretcher and related works
Paris, 2 November 1979 - Personal correspondence A copy of a letter Claude Picasso wrote to William Rubin, director of Painting and Sculpture at MoMA
Paris, 1 March 1975 - Personal correspondence Claude Picasso's letter to William S. Lieberman, dated 1 March 1975