1. Cadman, C. H., J. Hort. Sci., 31, 111 (1956).
2. Harrison, B. D., Nature, 178, 553 (1956).
3. Harrison, B. D., Ann. App. Biol., 45, 462 (1957).
4. Thomas, H. E., and Rawlins, T. E., in “Agric. Handbook”, 10, 53 (U.S. Dept. Agric., 1951).
5. Yarwood, C. E., and Thomas, H. E., Phytopath., 44, 511 (1954).