A.  Seilacher, ?Late Precambrian and early Cambrian Metazoa: preservational or real extinctions??, in Patterns of change in earth evolution, H. D.  Holland and Trendall, A. F., Eds. Berlin, Heidelberg, New York, Tokyo: Springer-Verlag, 1984, pp. 159-168.

Lv. Salvini-Plawen and Mayr, E., ?On the evolution of photoreceptors and eyes?, in Evolutionary Biology, vol. 10, M. K.  Hecht, Steere, W. C., and Wallace, B., Eds. New York and London: Plenum Press, 1977, pp. 207-263.