1. Stainer, R. Y., Donndroff, M., and Adelberg, E. A. (1986),The Microbial World, 5th ed., Prentice-Hall, New York.
2. Coackley, P. and O'Neill, J. (1975),Water Pollut. Control 74(4), 404–414.
3. Bucksteeg, W. (1966), Determination of sludge activity: a possibility of controlling activated sludge plants. Proceedings of the 3rd International Conference on Advances in Water Pollution Research, Munich, Germany.
4. Ghosh, S. G., Pohland, F. G., and Gates, W. E. (1972),J. Water Pollut. Control Fed. 44(3), 376–400.
5. Ghaly, A. E., Kok, R., and Ingrahm, J. M. (1989),Appl. Biochem. Biotechnol. 22, 59–77.