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
Gerti Fietzek (ed.), Cologne: Buchhandlung Walther König, 2009 - Essay Maria Eichhorn. The Artist's Contract