Question: What was Niel Barnard title during F. W. de Klerk state presidency from Aug 1989 to May 1994?
Sentence (from "F. W. de Klerk"): Frederik Willem de Klerk, DMS (] ; born 18 March 1936) is a South African politician who served as the country's State President from August 1989 to May 1994.
Relevant evidence: No