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2. Bloch, D. and Staves, M., 1986. Origins Life, 16: 309–310.
3. Branch, A.D., Benefeld, B.J. and Robertson, H.D., 1988. Proc. Nat. Acad. Sci. USA, 85: 9128–9132.
4. Branch, A.D. and Robertson, H.D., 1984. Science, 223: 450–455.
5. Branch, A.D., Robertson, H.D., and Dickson, E., 1981. Proc. Nat. Acad. Sci. USA, 78: 6381–6385.