Amsterdam, 28 January 1957 - Institutional correspondence Willem Sandberg's letter to Robert Giron, dated 28 January 1957
Amsterdam, 28 January 1957 - Institutional correspondence Willem Sandberg's letter to Bo Wennberg, dated 28 January 1957
Amsterdam, 18 April 1956 - Press release and communication Picasso's Guernica and studies will be at the Stedelijk Museum from mid-July to the end of September