1. J. Postgate , in Nitrogen Fixation, Cambridge University Press, Cambridge, 3rd edn, 1998, ch. 1, pp. 1–10
2. Personal ammonia sensor for industrial environments
3. S. Budarvari , in The Merck Index, An Encyclopedia of Chemicals, Drugs and Biologicals, ed. M. J. O'Neil, Royal Society of Chemistry, Cambridge, 12th edn, Merck, 1996
4. Optical Sensor for Gaseous Ammonia With Tuneable Sensitivity