1. Tustin, R. C., J. S. Afr. vet. med. Assoc., 40, 3–23 (1969).
2. Mackay, J. M. K., J. comp. Path., 79, 147–154 (1969).
3. Malmquist, W. A., Krauss, H. H., Moulton, J. E., and Wandera, J. G., Lab. Invest., 26, 528–533 (1972).
4. de Villiers, E.-M., Els, H. J., and Verwoerd, D. W., S. Afr. J. med. Scr., 40, 165–175 (1975).
5. Mackay, J. M. K., and Nisbet, D. I., in Oncogenesis and Herpesviruses (edit. by Briggs, P. M., de-Thé, G., and Payne, L. N.), 467–470 (International Agency for Research on Cancer, Lyons, 1972).