Jacobs, P.A.H.; Fourie, L.J.; Kok, D.J.(Published jointly by the Agricultural Research Council, ARC-Onderstepoort Veterinary Institute and the Faculty of Veterinary Science, University of Pretoria., 2001)
Fourie, L.J.; Kok, D.J.; Van Zyl, W.(Published jointly by the Agricultural Research Council, ARC-Onderstepoort Veterinary Institute and the Faculty of Veterinary Science, University of Pretoria., 2002)