New York, 9 September 1981 - Institutional correspondence An internal letter from Richard E. Oldenburg to staff at the Museum of Modern Art, New York
New York, 24 March 1980 - Institutional correspondence A letter from Richard Oldenburg and William Rubin to Javier Tusell
Madrid, 24 September 1936 - Institutional correspondence Letter from Josep Renau to Pablo Picasso, 24 September 1936