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
Hollywood, 21 October 1939 - Institutional correspondence H. Heyman's and G. E. Scheyer's letter to Sidney Janis