1. Argaw, N. Renewable energy in water and wastewater treatment applications NREL/SR-500-30383 June 2003. See http://www.nrel.gov.
2. Afghanistan: activity report: 2005;Asia Development Bank [ADB],2006
3. Inventory of ground-water resources in the Kabul basin, Afghanistan USGS;Broshears,2004
4. A simple high efficiency solar water purification system;Duff;Solar Energy,2005
5. Duff WS, “A Completely Passive, Valveless, Continuous Flow Solar Water Purification System” (2011); for the solar labs and Duff's work, see www.engr.colostate.edu.