Williams, R.; Schoeman, M.; Van Wyk, A.; Roos, K.; Josemans, E.J.(Published by the Agricultural Research Council, Onderstepoort Veterinary Institute, 1997)
Bowles, P.M.; Molloy, J.B.; Blight, G.W.; Singh, S.; Mabikacheche, L.G.(Published by the Agricultural Research Council, Onderstepoort Veterinary Institute ., 2000)