| usgs.gov | USGS Toxics Substances Hydrology Program |
| nutrientnet.org | Nutrient Net Demo |
| geocities.com | Waterose Personal Environmental Science Website |
| chesapeakebay.net | Nutrient Pollution |
| ncsu.edu | North Carolina State University Water Quality Group |
| usgs.gov | Usgs/nawqa: National Analysis Of Trace Elements In Ground Water, Streams, Sedim |
| lorchfoundation.org | The Lorch Foundation |
| livingwater.org.uk | Living Water |
| ceep-phosphates.org | CEEP - Centre Européen d'Etudes sur les Polyphosphates |
| usgs.gov | USGS National Analysis of Trace Elements |
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