1. Ball, J (1950). Lancet, 2, 520.
2. Black, R. L., Yielding, K. L., and Bunim, J. J. (1957). J. chronl. Dis., 5, 751.
3. Duthie, J. J. R., Brown, P. E., Knox, J. D. E., and Thompson, M. (1957). Ann. rheum. Dis., 16, 411. Empire Rheumatism Council (1955). Ibid., 14, 353.
4. Duthie, J. J. R., Brown, P. E., Knox, J. D. E., and Thompson, M. (1957). Ibid., 16, 277.
5. Gibson, H. J., and Ling, N. R. (1956). Ibid., 15, 246.