1. Arefev, O.A.; Zabrodina, M.N.; Makushina, V.M.; and Petrov, A.A. 1980. Relic tetra- and pentacyclic hydrocarbons in the old oils of the Siberian Platform. Izv. Akad. Nauk. SSR, Ser. Geol. 3: 135–140 (in Russian).
2. Awramik, S.M.; Schopf, J.W.; Walter, M.R.; and Buick, R. 1980. Filamentous fossil bacteria 3.5 Ga-old from the Archean of Western Australia. Science, in press.
3. Barghoorn, E.S.; Knoll, A.H.; Dembicki, H., Jr.; and Mein- schein, W.G. 1977. Variation in stable carbon isotopes in organic matter from the Gunflint Iron Formation. Geo- chim. Cosmochim. Acta 41: 425–430.
4. Barghoorn, E.S.; Meinschein, W.G.; and Schopf, J.W. 1965. Paleobiology of a Precambrian shale. Science 148: 461–472.
5. Bondesen, E.; Pedersen, K.R.; and Jørgensen, 0. 1967. Precambrian organisms and the isotopic composition of organic remains in the Ketilidian of South-West Greenland. Medd. Gr0nland 179 (4).