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
Mexico City, 26 September 1968 - Institutional correspondence Óscar Urrutia's telegram to Carol K. Uht
Madrid, 12 Julio 1971 - Institutional correspondence A letter from Juan Antonio Cánovas del Castillo to Florentino Pérez-Embid