1. Doll, R. Nature 265, 589–596 (1977).
2. W.H.O. Environmental Health Criteria No. 5 (1978).
3. Loveless, A. Nature 223, 206–207 (1969).
4. O'Connor, P. J., Saffhill, R. & Margison, G. P. in Environmental Carcinogens (eds Emmelot, P. & Kriek, E.) (Elsevier, Amsterdam, in the press).
5. Margison, G. P. & O'Connor, P. J. in Chemical Carcinogens and DNA (ed. Grover, P. L.) (CRC Press, West Palm Beach, in the press).