New York, 12 March 1956 - Institutional correspondence Bernard Karpel's letter to Willem Sandberg, dated 12 March 1956
Stockholm, 23 October 1956 - Institutional correspondence A letter from Bo Wennberg and K. G. Hulten to Pablo Picasso
New York, 27 November 1956 - Institutional correspondence Bernard Karpel's letter to Willem Sandberg, dated 27 November 1956