1. 1) Hanoi Clean Water Business Company: Assessment of Existing Groundwater Quality and treatment Effectiveness at the Water Treatment Plants managed by HCWBC, Report 2000
2. 2) Nhue, T. H., Tin, N. V., VietAnh, N., and Hai, D.: An assessment of the effectiveness of ammonia removal at water treatment in Hanoi City, Proceeding of Joint Seminar on TNRGW, 14-26 (2001)
3. 3) WHO: Guideline for drinking water quality. Vol. I, Recommendation. World Health Organization, Geneva, 2000.
4. 4) US EPA: Groundwater and Drinking water: Nitrification, U. S. Environmental Protection Agency, Washington, DC, (2005) http://www.epa.gov/safewater/tcr/pdf/nitrification.pdf
5. 5) Metcalf & Eddy, Inc.: Wastewater Engineering: Treatment/Disposal/Reuse, 2nd Edition, revised by George Tchobanoglous, McGraw-Hill, New York., pp. 696-716 (1979)