Pienaar, Juanita (Juanita Magrietha), 1965-; Du Plessis, Willemien (Wilhelmina), 1958-; Olivier, N.J.J. (Nicolaas Johannes Jacobus)(The Verloren van Themaat Centre for Public Law Studies, UNISA, 2012)
Duvel, G.H. (Gustav Heinrich)(South African Society for Agricultural Extension, Department of Agriculture, Ecomomics, Extensions and Rural Development, University of Pretoria, 2008)
Du Plessis, Willemien (Wilhelmina), 1958-; Pienaar, Juanita (Juanita Magrietha), 1965-; Olivier, N.J.J. (Nicolaas Johannes Jacobus)(The Verloren van Themaat Centre for Public Law Studies, UNISA, 2009)
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)