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
Madrid, 1981 - Conferences and articles Notes on the installation of Guernica and sketches in the Casón del Buen Retiro