Malan, F.S.; Wessels, C.D.(Published jointly by the Agricultural Research Council, ARC-Onderstepoort Veterinary Institute and the Faculty of Veterinary Science, University of Pretoria., 2001)
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)