Boomker, Jacob Diederik Frederik; Imes, G.D.; Cameron, Colin McKenzie; Naude, T.W.; Schoonbee, H.J.(Published by The Government Printer, Pretoria, 1979)
Pienaar, J. G.; Van der Westhuizen, G.C.A.; Anderson, L.A.P.; Naude, T.W.; Kellerman, T. Stephanus(Published by The Government Printer, Pretoria, 1976)