New York, 8 May 1968 - Institutional correspondence Antonio Serrano's letter to Fernando María Castiella
Madrid, 24 September 1936 - Institutional correspondence Letter from Josep Renau to Pablo Picasso, 24 September 1936
2 March 1974 - Institutional correspondence A letter from Karl Denim, S. S. Kush and Joshua Jericho in defence of Tony Shafrazi