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)
Botha, C.J. (Christoffel Jacobus); Kellerman, T. Stephanus; Schultz, R.A. (Rowena Anitra); Erasmus, G.L.; Retief, E.P.(Published by the Agricultural Research Council, Onderstepoort Veterinary Institute, 1998)