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
2 March 1974 - Institutional correspondence A letter from Karl Denim, S. S. Kush and Joshua Jericho in defence of Tony Shafrazi