Roxbury, 22 November 1955 - Institutional correspondence Alexander Calder's letter to Willem Sandberg, dated 22 November 1955
Roxbury, 12 January 1956 - Institutional correspondence Alexander Calder's letter to Willem Sandberg, dated 12 January 1956
Paris, 2 November 1979 - Personal correspondence A copy of a letter Claude Picasso wrote to William Rubin, director of Painting and Sculpture at MoMA
Paris, 1 March 1975 - Personal correspondence Claude Picasso's letter to William S. Lieberman, dated 1 March 1975