1. APHA , 1976 . Standard Methods for Examination of Water and Waste Water . 14th ed. American Public Health Association, 1740 Broadway, New York, NY1740 .
2. The Action of Filter Aids
3. CFR, 1987 . Code of Federal Regulations . 9 (III ):381.66 , U.S. Govt. Printing Office, Washington, D.C.