Marasas, Walter F.O. (Walter Friedrich Otto); Kellerman, T. Stephanus; Gelderblom, W.C.A.; Thiel, P.G.; Van der Lugt, Jaco J.(Published by the Government Printer, Pretoria., 1988)
Kellerman, T. Stephanus; Marasas, Walter F.O. (Walter Friedrich Otto); Thiel, P.G.; Gelderblom, W.C.A.; Cawood, M.(Published by the Government Printer, Pretoria., 1990)