1. A potential phosphate crisis;Abelson;Science,1999
2. BAM (Federal Institute for Materials Research and Testing). 2005. Sustainable and safe re-use of municipal sewage sludge for nutrient recovery â SUSAN. . Accessed February 2009.
3. BMBF/BMU (Bundesministerium für Bildung und Forschung/Bundesministerium für Umwelt, Naturschutz und Reaktorsicherheit) Funding Programme. 2008. Recycling management of plant nutrients, especially phosphorus. . Accessed February 2009.
4. Closing the phosphorus loop;Christen;Environmental Science and Technology,2007
5. Dissolution behavior of nutrition elements from steelmaking slag into seawater;Futatsuka;ISIJ International,2004