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
Paris, 3 November 1980 - Institutional correspondence Dominique Bozo's letter to Josep Lluís Sert, dated 3 November 1980
Paris, 23 December 1980 - Institutional correspondence Dominique Bozo's letter to Josep Lluís Sert, dated 23 December 1980