1. Clube, S.V.M., and Napier W.M. (1982) ‘Spiral arms, comets and terrestrial catastrophism’, Quart. J. Roy. Astron. Soc. 23, 45–66.
2. Clube, S.V.M. and Napier, W.M. (1984) ‘Comet capture from molecular clouds: A dynamical constraint on star and planet formation’, Monthly Not. Roy. Astron. Soc. 208, 575–588.
3. Cameron, A.G.W. (1973) ‘Accumulation processes in the primitive solar nebul’, Icarus 18, 407–450.
4. Cameron, A.G.W. (1978) ‘The primitive solar accretion disk and the formation of the planets’, in S.F. Dermott (ed.), The Origin of the Solar System, New York, pp. 49–75.
5. Donn, B. (1976) ‘Comets, interstellar clouds, and star clusters’, in The Study of Comets, NASA SP-393, Washington, pp. 663–672.