Amsterdam, 8 November 1955 - Institutional correspondence Willem Sandberg's letter to Josep Lluís Sert
Amsterdam, 11 October 1955 - Institutional correspondence Willem Sandberg's letter to Daniel-Henry Kahnweiler, dated 11 October 1955
Amsterdam, 8 November 1955 - Institutional correspondence Willem Sandberg's letter to Alexander Calder, dated 8 November 1955
Amsterdam, 30 November 1955 - Institutional correspondence Willem Sandberg's letter to Alexander Calder, dated 30 November 1955
Amsterdam, 2 December 1955 - Personal correspondence Willem Sandberg's letter to Maurice Lefebvre-Foinet, dated 2 December 1955
Amsterdam, 3 December 1955 - Institutional correspondence Willem Sandberg's letter to Dora Maar, dated 3 December 1955
Amsterdam, 9 December 1955 - Personal correspondence Willem Sandberg's letter to Maurice Lefebvre-Foinet, dated 9 December 1955
Amsterdam, 16 December 1955 - Institutional correspondence Willem Sandberg's letter to Dora Maar, dated 16 December 1955
Amsterdam, 27 December 1955 - Institutional correspondence Willem Sandberg's letter to l'Association Française d'Action Artistique
