1. T. J. Bardos, N. Datta Gupta, P. Hebborn and D. J. Triggle, J. Med. Chem. 8, 167 (1965).
2. M. C. Berenbaum and M. Calley, Nature (London) 196, 656 (1962).
3. M. Beroza and A. B. Borkovec, J. Med. Chem. 7, 44 (1964).
4. A. Bloch, Biochim. Biophys. Acta 201, 323 (1970).
5. W. F. Chamberlain and C. C. Barrett, Nature (London) 218, 471 (1968).