Pereira, M.F.V.T.; Williams, M.; Du Preez, W.B(Journal for New Generation Sciences, Vol 8, Issue 2: Central University of Technology, Free State, Bloemfontein, 2010)
Hua, T.; Sowe, M.; Van Niekerk, T.I.; Holdack-Ianssen, H.; Du Preez, K.; Pienaar, S.(Journal for New Generation Sciences, Vol 8, Issue 1: Central University of Technology, Free State, Bloemfontein, 2010)