Ekosse, G.E.; De Jager, L.; Van Den Heever, D.(Journal for New Generation Sciences, Vol 7, Issue 2: Central University of Technology, Free State, Bloemfontein, 2009)
Kuhn, C.; De Lange, R; De Beer, D.J.(Journal for New Generation Sciences, Vol 7, Issue 2: Central University of Technology, Free State, Bloemfontein, 2009)
De Villiers, J.C.; Botma, Y; Seale, I(Journal for New Generation Sciences, Vol 7, Issue 2: Central University of Technology, Free State, Bloemfontein, 2009)
Barnes, H.; DZansi, D.; Wilkinson, A.; Viljoen, M.(Journal for New Generation Sciences, Vol 7, Issue 2: Central University of Technology, Free State, Bloemfontein, 2009)