1. Variations in the global phosphorus cycle;Compton,2000
2. Phosphates recovery for recycling from sewage and animal wastes;Driver;Phosphorus and Potassium,1998
3. Source Apportionment of Nitrogen and Phosphorus Inputs into the Aquatic Environment,2005
4. The phosphorus cycle;Emsley,1980
5. FAO (2006) FAOSTAT. Statistics Division, Food and Agriculture Organization of the United Nations.