1. Ballio, A., Chain, E. B., Dentice di Accadia, F., Rolinson, G. N., and Batchelor, F. R., Nature, 183, 180 (1959).
2. Sheehan, J. C., Henery-Logan, K. R., and Johnson, D. A., J. Amer. Chem. Soc., 75, 3292 (1953).
3. “The Chemistry of Penicillin”, 481 (Princeton University Press, 1949).
4. Szabo, J. L., and Bruce, W. F., U.S. Patent 2,627,491; Chem. Abst., 48, 734 (1954).
5. Hockenhull, D. J. D., Ramachandran, K., and Walker, T. K., Arch. Biochem., 23, 160 (1949). Burger, A., “Medicinal Chemistry”, 2, 880 (Interscience Pub., 1951). Kato, T., Kagaku (Science), 23, 217 (1953); J. Antibiotics (Japan), 6, A, 130, 184 (1953). Abraham, E. P., Giornale di Microbiologica, 2, 102 (1956). Arnstein, H. R. V., and Crawhall, J. C., Biochem. J., 67, 180 (1957).