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
25 September and 11 October 1972 - Personal correspondence A letter from Catherine Freedberg to Roland Penrose, including the reply
Cambridge, Massachusetts, 14 May 1973 - Institutional correspondence Catherine Freedberg's letter to Patricia Failing