1. Ermler, U., Grabarse, W., Shima, S., Goubeaud, M. & Thauer, R. K. Science 278, 1457–1462 (1997).
2. Woese, C. R. & Wolfe, R. S. Nature 19, 273–274 (1986).
3. Ferry, J. G. (ed.) Methanogenesis — Ecology, Physiology, Biochemistry and Genetics (Chapman & Hall, New York, 1993).
4. Hogan, K. B., Hoffman, J. S. & Thompson, A. M. Nature 354, 181–182 (1991).
5. Rosenzweig, A. C., Frederick, C. A., Lippard, S. J. & Nordlund, P. Nature 366, 537–543 (1993).