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
Barcelona, 4 February 1938 - Institutional correspondence Correspondence regarding the organisation of a Picasso exhibition in the USA