Kriek, N.P.J.; Keet, D.F.; Raath, J.P.; De Vos, Valerius; Huchzermeyer, Hildegard F.A.K.; Bengis, Roy G.(Published by the Agricultural Research Council, Onderstepoort Veterinary Institute, 1996)
Van Aswegen, G.; De Vos, Valerius; Schoeman, J.H.; Van Noorden, Susan; Kotze, Sanet H.(Published by the Agricultural Research Council, Onderstepoort Veterinary Institute, 1996)