1. Adams, S. S., Cliffe, E. E., Lessel, B., and Nicholson, J. S. (1963). Nature (Lond.), 200, 271.
2. Sequential Medical Trials;Armitage, P.,1960
3. Chalmers, T. M. (1963). Ann. rheum. Dis., 22, 358.
4. Drivsholm, Aa., and Madsen, S. (1961). Scand. J. clin. Lab. Invest., 13,442.
5. Hajnal, J., Sharp, J., and Popert, A. J. (1959). Ann.