Botha, C.J. (Christoffel Jacobus); Schultz, R.A. (Rowena Anitra); Van der Lugt, Jaco J.; Retief, E.; Labuschagne, Leonie(Published by the Agricultural Research Council, Onderstepoort Veterinary Institute, 1999)
Du Plessis, D.H.; Van Wyngaardt, Wouter; Romito, M.; Du Plessis, M.(Pretoria : Agricultural Research Council, Onderstepoort Veterinary Institute, 1999)