1. Bienenstock, J., 1974. In: L. Brent and J. Holborow (Editors), Progress in Immunology II, 4: 197. North Holland Publishing Co.
2. Bohl, E. H. and Saif, L. J., 1975. Infect. and Immun., 11: 23.
3. Bourne, F. J., 1973. Proc. Nutr. Soc., 32:205.
4. Bourne, F. J., and Curtis, J., 1973. Immunology, 24:157.
5. Bourne, F. J., Newby, T. J. and Chidlow, J. W., 1975. Res. Vet. Sci., 18:244.