Du Plessis, D.H.; Van Wyngaardt, Wouter; Gerdes, Gertruida Hermanna; Opperman, E.(Published by the Agricultural Research Council, Onderstepoort Veterinary Institute., 1991)
Zandbergen, Thijs A.; Van de Wiel, Paul A.; De Groot, Mia; Uilenberg, Gerrit(Published by the Agricultural Research Council, Onderstepoort Veterinary Institute., 1991)
Scholtz, M.M.; Spickett, Arthur M.; Lombard, P.E.; Enslin, C.B.(Published by the Agricultural Research Council, Onderstepoort Veterinary Institute., 1991)