1. RB Alexander, JR Slack, and AS Ludtke .et al.1998 .Data from selected US Geological Survey national stream water quality monitoring networks .Water Resour Res,34:2401 -05 .
2. S. Blomqvist, A. Gunnars, and R. Elmgren .2004 .Why the limiting nutrient differs between temperate coastal seas and freshwater lakes: a matter of salt .Limnol Oceanogr,49:2236 -41 .
3. DF Boesch .2004 .The Gulf of Mexico's dead zone .Science,306:977 -78 .
4. SR Carpenter, NF Caraco, and DL Correll .et al.1998 .Nonpoint pollution of surface waters with phosphorus and nitrogen .Ecol Appl,8:559 -68 .
5. WK Dodds .1993 .What controls levels of dissolved phosphate and ammonium in surface waters? Aquat Sci,55:132 -42 .