Amsterdam, 16 November 1953 - Institutional correspondence Willem Sandberg's letter to Pablo Picasso, dated 16 November 1953
Rome, 18 February 1954 - Institutional correspondence Eugenio Reale's letter to Pablo Picasso, dated 18 February 1954
New York, 10 March 1955 - Institutional correspondence Alfred H. Barr Jr.'s letter to Pablo Picasso, dated 10 March 1955
Paris, 29 September 1955 - Institutional correspondence Daniel-Henry Kahnweiler's letter to Willem Sandberg, dated 29 September 1955
Amsterdam, 8 November 1955 - Institutional correspondence Willem Sandberg's letter to Josep Lluís Sert
Paris, 30 January 1964 - Institutional correspondence A letter from the Committee of the exhibition España Libre (Free Spain) to Pablo Picasso
Madrid, 9 December 1975 - Institutional correspondence A letter from the general director of Artistic and Cultural Heritage, from Spain's Ministry of General Education
