1. Asscher, A. W., Sussman, M., Waters, W. E., Davis, R. H., and Chick, S. (1966). Lancet, 2, 1037.
2. Chard, T., and Cole, P. G. (1963). Ibid., 2, 326.
3. Constable, P. J. (1966). Ibid., 2, 195.
4. Deutch, M., and Jespersen, H. G. (1964). Acta med. Scand., 174, 191.
5. Fairley, K. F., and Barraclough, M. (1966). Med. J. Aust., 1, 93.