Amsterdam, 25 January 1956 - Transport documents M. Winter's letter to Robert Giron, dated 25 January 1956
Amsterdam, 25 January 1956 - Institutional correspondence M. Winter's letter to Robert Giron, dated 25 January 1956
Ellen C. Oppler (ed.), <em>Picasso’s Guernica</em>, New York and London: W. W. Norton & Company, 1988, 236–238 - Essay “How Effective Is Social Protest Art? (Vietnam)”
Siracusa, New York, 15 July 1979 - Institutional correspondence Ellen Oppler's letter to Luisa Kreisberg