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
Stockholm, 27 October and 1 de November 1956 - Institutional correspondence Memos of Swedish Foreign Ministry about the catalogue and exhibition Guernica