Sao Paulo, 25 March 1985 and Madrid, 2 April 1985 - Institutional correspondence The loan of Guernica denied for Brazil exhibition
Madrid, 15 March 1986 - Institutional correspondence Letter from Alfonso E. Pérez Sánchez to Dionisio Hernández Gil
New York and Madrid, June 1988 - Institutional correspondence Correspondence between William Rubin and Alfonso E. Pérez Sánchez
1988-1989 - Institutional correspondence Correspondence related to the Guernica exhibition project at the Museum Boymans-van Beuningen in Rotterdam
August-September 1990 - Institutional correspondence Correspondence on an exhibition project in Hiroshima
New York, 22 November 1969 - Institutional correspondence A letter from William S. Lieberman to Roland Dumas
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, 7 June 1977 - Institutional correspondence William S. Lieberman's letter to Richard Oldenburg, dated 7 June 1977
New York, 1 June 1977 - Institutional correspondence William S. Lieberman's letter to Richard Oldenburg, dated 1 June 1977
New York, 31 May 1977 - Institutional correspondence William S. Lieberman's letter to Richard Oldenburg, dated 31 May 1977
New York, 5 July 1956 - Institutional correspondence William S. Lieberman's letter to Richard Griffith