1. Bergey's Manual of Determinative Bacteriology, and Eds. (Williams and Wilkens, Baltimore, 1974), 8th ed., Chap. 12.
2. and Fundamentals of Microbiology (Saunder, Philadelphia, 1974), 9th ed.
3. Environmental Protection Agency, Process Design Manual for Nitrogen Control (U. S. GPO, Washington, D. C., 1975).
4. Nitrification and nitrogen removal