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
Hollywood, 21 October 1939 - Institutional correspondence H. Heyman's and G. E. Scheyer's letter to Sidney Janis