1. Appleby C A, Bergersen F J, May Ching T, Gibson A H, Greshoff P M and Trinick M J 1981 Cytochromes of rhizobia from Parasponia, pea and soybean nodules, and from nitrogen fixing continuous cultures.In Current Perspectives in Nitrogen Fixation (4th Int. Symposium on Nitrogen Fixation, Canberra, eds. Gibson A H and Newton W E). Elsevier/North-Holland Biomedical Press, Amsterdam, p. 369.
2. Appleby C A, Tjepkema J D and Trinick M J 1983 Haemoglobin in a non-leguminous plant, Parasponia: Possible genetic origin and function in nitrogen fixation. Science 200, 951–953.
3. Becking J H 1983 TheParasponia parviflora — Rhizobium symbiosis — Host specificity, growth and nitrogen fixation under various conditions. Plant and Soil 75, 309–342.
4. Bergersen F J 1982 Root nodules of legumes: Structures and Functions. Research Studies Press, John Wiley and Sons Ltd, New York.
5. Bond G 1960 Inhibition of nitrogen fixation in non-legume root nodules by hydrogen and carbon monoxide. J. Exp. Bot. 11, 91–97.