Madrid, 21 February 1969 - Institutional correspondence Florentino Pérez-Embid's letter to Joaquín de la Fuente
Madrid, 17 February 1986 - Institutional correspondence Letter from Justino Azcárate to Carmen Crespo
New York, 20 October 1939 - Institutional correspondence Anne Beidberg's letter to Alfred H. Barr Jr.