1. Bohstedt, G., and Dickson, J. G., Phytopathology, 20, 132 (1930).
2. Mundkur, B. B., Phytopathology, 24, 1237 (1934).
3. Prentice, N., Dickson, A. D., and Dickson, J. G., Nature, 184, 1319 (1959).
4. Kurmanov, I. A., Trudy vses Inst. vet. Sanit., 23, 187 (1964).
5. Forgacs, J., and Carll, W. T., Advances in Veterinary Science, 7, 273 (1962).