1. Roberts, K. and Siegel, S.: 1967, Plant Physiol. 42, 1215.
2. Siegel, S. M.: 1973, Environmental Biol. and Medicine 2, 19.
3. Puerner, N. and Siegel, S.: 1976, Life Sci. and Space Res. XIV, 363.
4. Galun, M., Feldstein, H., Keller, P., Malki, D., Galun, E., Siegel, S., and Siegel, B.: 1983, Water, Air, and Soil Pollution 22, in press.
5. Tsezos, M. and Volesky, B.: 1981, Biotechnology and Bioengineering 24, 385.