1. Alvin, K. L., Spicer, R. A., and Watson, J., 1978, A Classopollis-containingmale cone associated with Pseudofrenelopsis, Palaeontology 21: 847–856.
2. Andrews, H. N., 1963, Early seed plants, Science 142: 925–931.
3. Andrews, H. N., Gensel, P. G., and Forbes, W. H., 1974, An apparently heterosporous plant from the Middle Devonian of New Brunswick, Palaeontology 17: 387–408.
4. Averitt, P., 1975, Coal resources of the United States, January 1, 1974, U.S. Geol. Surv., Bull.1412: 1–131.
5. Avise, J. C., 1976, Genetic differentiation during speciation, in: Molecular Evolution( F. J. Ayala, ed.), pp. 106–122, Sinauer Associates, Sunderland, Mass.