27 May 1977
References
Muller, C.F.J. (ed)(1981). Five Hundred years: a history of South Africa; 3rd rev. ed Pretoria: Academica, p. 520.|Kalley, J.A.; Schoeman, E. & Andor, L.E. (eds)(1999). Southern African Political History: a chronology of key political events from independence to mid-1997, Westport: Greenwood.