1. Buss, L. W. The Evolution of Individuality (Princeton Univ. Press, NJ, 1987).
2. Han, T.-M. & Runnegar, B. Megascopic eukaryotic algae from the 2.1 billion-year-old Negaunee Iron-Formation, Michigan. Science 257, 232–235 (1992).
3. Knoll, A. H. The early evolution of eukaryotes: a geological perspective. Science 256, 622–627 (1992).
4. Whittington, H. B. The Burgess Shale (Yale Univ. Press, New Haven, CT, 1985).
5. Briggs, D. E. G., Erwin, D. H. & Collier, F. J. The Fossils of the Burgess Shale (Smithsonian Institution Press, Washington DC, 1994).