Grant, C.C. (Catharina Cornelia); Biggs, H.C.; Meissner, H.H.; Basson, P.A.(Published by the Agricultural Research Council, Onderstepoort Veterinary Institute, 1996)
Du Plessis, D.H.; Van Wyngaardt, Wouter; Gerdes, Gertruida Hermanna; Opperman, E.(Published by the Agricultural Research Council, Onderstepoort Veterinary Institute., 1991)