Van Amstel, S.R.; Myburgh, Elsbe; Mundell, Jennifer; Davidson, B.(Published by the Agricultural Research Council, Onderstepoort Veterinary Institute, 1994)
Van Amstel, S.R.; Reyers, Fred; Myburgh, Elsbe; Pretorius, Gertruida; Sacks, P.(Published by the Agricultural Research Council, Onderstepoort Veterinary Institute, 1994)