1- American Water Works Association (2003). “A brief history of drinking water.” <http://www.awwa.org/advocacy/pressroom/bhist-1. cfm> (Apr. 2, 2006).
2- Huisman, L., and Wood, W. E. (1974). Slow sand filtration, World Health Organization, Geneva, Switzerland.
3- Bellamy, W. D., Hendricks, D. W., and Longsdon, G. S. (1985). “Slow sand filtration: Influences of selected process variables.” J. AWWA, 77(12), 62-66.
4- Gray & Osborne Inc. (1995). “Evaluation of crushed recycled glass as a filtration medium in slow sand filtration.” <http://www.cwc.org/glass/gl954rpt.pdf> ( May 5, 2006).
5- Bellamy, W. D., Silverman, G. P., Hendricks, D. W., and Longsdon, G. S. (1985). “Removing giardia cysts with slow sand filtration.” J. AWWA, 77(2), 53-60.