1. Niklas, K. J., Tiffney, B. H. & Knoll, A. H. in Phanerozoic Diversity Patterns: Profiles in Macroevolution (ed. Valentine, J. W.) 97–128 (Princeton Univ. Press, New Jersey, 1985).
2. Knoll, A. H. in Community Ecology (eds Diamond, J. & Case, T. J.) 126–141 (Harper & Row, New York, 1986).
3. Crane, P. R. in The Origins of Angiosperms and their Biological Consequences (eds Friis, E. M., Chaloner, W. G. & Crane, P. R.) 107–144 (Cambridge Univ. Press, UK, 1987).
4. Hickey, L. J. Am. J. Bot. 78, 115 (1991).
5. Love, J. D. & Christiansen, A. C. Geological Map of Wyoming (US Geological Survey, 1985).