Cloud, P. E., 1983, The biosphere: Scientific American, v. 249, no. 3, p. 176-
189.
Schopf, J. W., 1983, Earth's Earliest Biosphere: Its Origin and Evolution:
Princeton, New Jersey, Princeton University Press.
Schopf, J. W., Hayes, J. M., and Walter, M. R., 1983, Evolution of Earth's
Earliest Ecosystems: Recent Progress and Unsolved Problems, in Schopf,
J. W., ed., Earth's Earliest Biosphere: Its Origin and Evolution:
Princeton, New Jersey, Princeton University Press, p. 361-384.