New York, 12 March 1956 - Institutional correspondence Bernard Karpel's letter to Willem Sandberg, dated 12 March 1956
New York, 27 November 1956 - Institutional correspondence Bernard Karpel's letter to Willem Sandberg, dated 27 November 1956
New York, 8 April 1981 - Press release and communication A press release from New York's Museum of Modern Art concerning a Spanish delegation's request to send Guernica to Spain