Amsterdam, 23 May 1956 - Institutional correspondence Willem Sandberg's letter to Bo Wennberg, dated 23 May 1956
Amsterdam, 15 September 1956 - Institutional correspondence Willem Sandberg's letter to Bo Wennberg, dated 15 September 1956
Amsterdam, 9 October 1956 - Institutional correspondence Willem Sandberg's letter to Bo Wennberg, dated 9 October 1956
Amsterdam, 15 October 1956 - Institutional correspondence Willem Sandberg's letter to Bo Wennberg, dated 15 October 1956
Amsterdam, 27 February 1956 - Institutional correspondence Willem Sandberg's letter to Robert Giron, dated 27 February 1956
Amsterdam, 10 December 1956 - Institutional correspondence Willem Sandberg's letter to Robert Giron, dated 10 December 1956
