London, 18 April 1980 - Institutional correspondence Nicholas Serota's letter to Roland Penrose, dated 18 April 1980
London, 1 May 1980 - Institutional correspondence Nicholas Serota's letter to Roland Penrose, dated 1 May 1980
Madrid, 1 September 1977 - Institutional correspondence A letter from Jesús Madalena to José Mario Armero
New York, February 24, 1970 - Letter A letter from Walter Bareiss and Robert Von Berg to Wilder Green