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
New York, 20 October 1939 - Institutional correspondence Anne Beidberg's letter to Alfred H. Barr Jr.