1. Ball, J. (1950). Lancet, 2, 520.
2. in preparation;Ball, J.; Lawrence, J.S.;Ann. rheum. Dis,1961
3. Kellgren, J. H., and Lawrence, J. S. (1956). Ibid., 15, 1. and Aitken-Swan, J. (1953). Ibid., 12, 5.
4. Lawrence, J. S., and Bennett, P. H. (1960). Ibid., 19, 20.
5. Laine, V., and de Graaff, R. (1961). Proc. roy. Soc. Med. In the press.