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)
Kellerman, T. Stephanus; Maartens, B.P.; Schultz, R.A. (Rowena Anitra); Swart, D. Petro(Published by the Agricultural Research Council, Onderstepoort Veterinary Institute, 1994)