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)
Doyer, O.T.; D'Haese, M.F.C. (Marijke); Kirsten, Johann F.; Van Rooyen, C.J. (Cornelius Johannes)(Agricultural Economics Association of South Africa, 2007-12)