1. Chapter 4. Utilization and Metabolism of Nitrogen by Humans, in Nitrogen in the Environment: Sources, Problems and Management;Follett,2008
2. How a century of ammonia synthesis changed the world;Erisman;Nature Geosci.,2008
3. Yara Fertilizer Industry Handbook, February 2014;YARA,2014
4. Ullmann's Encyclopedia of Industrial Chemistry, vol. 11, Chapter 2,2012
5. The contribution of commercial fertilizer nutrients to food production;Stewart;Agron. J.,2005