1. Allen, M. B.: General features of algal growth in sewage oxidation ponds. Calif. State Water Pollution Control Board Publication No. 13 (1955).
2. Arnon, D. I., P. S. Ichioka, G. Wessel, A. Fujiwara and J. T. Woolley: Physiol. Plantarum 8, 538 (1955).
3. Association of Official Agricultural Chemists. Official Methods of Analysis. 7th ed. Washington (1950).
4. Cheftel, R. I., R. Munier et M. Macheboeuf: Bull. Soc. Chim. biol. (Paris) 133, 840 (1951).
5. Consden, R., A. H. Gordon and A. J. P. Martin: Biochemic. J. 38, 224 (1944).