1. Phosphorus availability in the 21st century;Steen;Phosphorus and Potassium, September-October,1998
2. The story of phosphorus: Global food security and food for thought;Cordell;Global Environmental Change,2009
3. IFDC, 2010. World phosphate rock reserves and resources. ISBN 978-0-88090-167-3.
4. Miljøministeriet (2013), Danmark uden affald, Genanvend mere - fobrænd mindre. 2013/14:2, ISBN: 978-87-93026-07-0.
5. Dutch analysis for P-recovery from municipal wastewater;Roeleveld;Water Science and Technology,2004