1. Simmons, J. L., thesis, Goucher College Library, Towson, Md. (1958).
2. Van Lanen, J. M., and Tanner, F. W., Vitamins and Hormones, 6, 163 (1948).
3. Funk, H. B., Krulwich, T. A., and Guttman, H. N., Bact. Proc., 9 (1964).
4. Fuller, R. C., Anderson, I. C., and Nathan, H. A., Proc. U.S. Nat. Acad. Sci., 44, 239 (1958).
5. Guttman, H. N., in Analytical Microbiology (edit. by Kavanagh, F.), 527(Academic Press, N.Y., 1963).