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)
Swan, Gerry E.; Schultz, R.A. (Rowena Anitra); Kellerman, T. Stephanus; Mulders, M.S.G.; Maartens, B.P.; Van der Walt, J.J.(Published by the Agricultural Research Council, Onderstepoort Veterinary Institute, 1995)