20 February 1980 - Institutional correspondence A letter from Ricardo de la Cierva Hoces to Adolfo Suárez
Madrid, 28 June 1980 - Institutional correspondence Ricardo de la Cierva Hoces' letter to Javier Tusell
18 May 1940 - Internal museum documents Circulating exhibition contract for Picasso: Forty Years of His Art (second edition) between the Museum of Modern Art, New York, and the Carnegie Institute