1. Baker, J. R., and Ransom, R. M., Proc. Roy. Soc., B, 110, 313 (1932).
2. Dobie, J. B., Carver, J. S., and Roberts, J., Bull. Wash. State Agric. Exp. Sta., No. 471 (1946). Weber, W. A., Proc. 9th World's Poult. Congr., 2, 99 (Paris, 1951).
3. Whetham, E. O., J. Agric. Sci., 23, 383 (1933).
4. Hutchinson, J. C. D., in “Progress in the Physiology of Farm Animals”, edit. Hammond, J., 1, chapter 7 (London, 1954).
5. Temperton, H., Press Conference, National Institute of Poultry Husbandry, Newport, Shropshire (1955).