Madrid, 6 December 1968 - Institutional correspondence Luis Carrero Blanco's letter to Florentino Pérez Embid
New York, 8 May 1968 - Institutional correspondence Antonio Serrano's letter to Fernando María Castiella
ca. 1981 - Newspapers The Guernica Imbroglio. Al international Tug-of-War over Picasso's Protest Painting