Paris, 17 May 1956 - Personal correspondence Daniel-Henry Kahnweiler's letter to Pablo Picasso, dated 17 May 1956
New York, 7 March 1956 - Institutional correspondence William S. Lieberman's letter to Porter McCrary
New York, 20 September 1956 - Institutional correspondence William S. Lieberman's letter to Alfred H. Barr Jr.
New York, 5 July 1956 - Institutional correspondence William S. Lieberman's letter to Richard Griffith