Brussels, 10 November 1955 - Institutional correspondence Robert Giron's letter to Willem Sandberg, dated 10 November 1955
Brussels, 17 February 1956 - Institutional correspondence Robert Giron's letter to Willem Sandberg, dated 17 February 1956
Brussels, 25 February 1956 - Institutional correspondence Robert Giron's letter to Willem Sandberg, dated 25 February 1956
Brussels, 28 March 1956 - Insurance documents Robert Giron's letter to Willem Sandberg, dated 28 March 1956
Brussels, 10 April 1956 - Institutional correspondence Robert Giron's letter to Willem Sandberg, dated 10 April 1956
Brussels, 4 April 1956 - Institutional correspondence Robert Giron's letter to Willem Sandberg, dated 4 April 1956
Brussels, 7 May 1956 - Institutional correspondence Robert Giron's letter to Willem Sandberg, dated 7 May 1956
Brussels, 6 December 1956 - Institutional correspondence Robert Giron's letter to Willem Sandberg, dated 6 December 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)”
Brussels, 22 December 1955 - Institutional correspondence Robert Giron's letter to Alfred H. Barr Jr.
Siracusa, New York, 15 July 1979 - Institutional correspondence Ellen Oppler's letter to Luisa Kreisberg