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)
Gallivan, Gordon J.; De Vos, Valerius(Published jointly by the Agricultural Research Council, ARC-Onderstepoort Veterinary Institute and the Faculty of Veterinary Science, University of Pretoria., 2003)