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
ca. 1960–1964 - Newspapers Press cutting with a photograph of the replica Guernica tapestry and Nelson Rockefeller, along with a brief text on his collection