1. Monitoring Water Quality in the Future;de Zwart,1995
2. http://ncseonline.org/NLE/CRSreports/07Jan/RL33466.pdf
3. Water Quality Issues in the 111th Congress: Oversight and Implementation; Congressional Research Service Reports;Copeland,2009
4. The EU water framework directive: Measures and implications;Kallis;Water Policy,2001