1. (2010) European Pharmacopoeia, 7th edn.
2. (2009) British Pharmacopoeia
3. (2008) US Pharmacopeia, 32nd edn., USA
4. Welch Ch, Wu N, Biba M, Hartman R, Brekovic T, Gong X, Helmy R, Schafer W, Cuff J, Pirzada Z, Zhou L (2010) Trends Anal Chem 29:667–680
5. Anastas PT, Warner JC (2000) Green chemistry: theory and practice. Oxford University Press, USA