1. Kirk, E., Gastroenterology, 12, 782 (1949).
2. Studies by Dr. J. J. Enright, cited by Hedin, P. A., and Adachi, R. A., J. Nutrit., 77, 229 (1962).
3. Costa, G., Ullrich, L., Kantor, F., and Holland, J. F., Clin. Res., 13, 320 (1965).
4. Sheffner, A. L., Eckfeldt, G. A., and Spector, H., J. Nutrit., 60, 105 (1956).
5. Isselbacher, K. J., Amer. J. Clin. Nutrit., 5, 527 (1957).