Vorster, H.J. (Halina Johanna); Stevens, Joseph Benjamin; Steyn, Gert Jacobus(South African Society for Agricultural Extension, Department of Agriculture, Ecomomics, Extensions and Rural Development, University of Pretoria, 2008)
Viljoen, Jozua Jakobus; Ganswindt, Andre; Palme, Rupert; Reynecke, Hendrik C.; Du Toit, Johan T.; Langbauer, William Richard(South African National Parks, 2008)