1. Martin, P. S. & Mehringer, P. J. Jr in The Quaternary of the United States (eds Wright, H. E. & Frey, D. G.) 433–451 (Princeton University Press, 1965).
2. Adams, J. M., Faure, H., Faure-Denard, L. McGlade, J. M. & Woodward, F. I. Nature 348, 711–714 (1990).
3. Schlesinger, W. H. Soil Sci. 133, 247–255 (1982).
4. Whittaker, R. H. & Niering, W. A., Ecology 56, 771–790 (1975).
5. Ehleringer, J. & Mooney, H. A. in Encyclopedia of Plant Physiology, New Ser. 12D, 205–231 (1983).