Greyling, Barend Jacobus; Kryger, Per; Du Plessis, S.; Van Hooft, W.F.; Van Helden, Paul David; Getz, Wayne Marcus; Bastos, Armanda D.S.(Academic Journals, 2008)
Steenkamp, Gerhardus; Ferguson, Jan Willem Helenus; Boy, Sonja Catharina; Ferreira, Sam M.; Bester, Marthan Nieuwoudt(South African Veterinary Association, 2008-03)