De Boer, Ann-Louise; Du Toit, Pieter Hertzog; Bothma, T.J.D. (Theodorus Jan Daniel)(Vaal Triangle Faculty of Northwest University in South Africa, 2015-11)
Kroeze, J.H. (Jan Hendrik); Bothma, T.J.D. (Theodorus Jan Daniel); Matthee, Machdel C.(Vaal Triangle Faculty of Northwest University in South Africa, 2010-07)