Amsterdam, 16 November 1953 - Institutional correspondence Willem Sandberg's letter to Pablo Picasso, dated 16 November 1953
Paris, 9 June 1953 - Institutional correspondence Maurice Jardot's letter to Francisco Matarazzo Sobrinho
Amsterdam, 5 May 1953 - Institutional correspondence Willem Sandberg's letter to Eugenio Reale, dated 5 May 1953
Amsterdam, 18 August 1953 - Institutional correspondence Willem Sandberg's letter to Eugenio Reale, dated 18 August 1953
Amsterdam, 11 September 1953 - Institutional correspondence Willem Sandberg's letter to Fernanda Wittgens
20 September 1954 - Institutional correspondence Maurice Jardot's letter to Jaime Sabartés, dated 20 September 1953