Olivier, P.A.S.; Dippenaar, Susan M.; Khalil, L.F.; Mokgalong, N.M.(Published by the Agricultural Research Council, Onderstepoort Veterinary Institute ., 2000)
Swan, Gerry E.; Oliver, D.W.; Van Rensburg, J.; Steyn, H.S.; Mulders, M.S.G.(Published by the Agricultural Research Council, Onderstepoort Veterinary Institute ., 2000)