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
Mexico City, 21 April 1944 - Institutional correspondence A letter from Luis de Zulueta to Jorge Enciso