1. United States Pharmacopeia and National Formulary (USP 38-NF 33). Chapter <231>Heavy metals. Accessed August 26, 2015, at: www.usp.org.
2. Harmonization of the USP, EP and JP heavy metals testing procedures;Blake;USP Pharmacopeial Forum,1995
3. Guideline on the specification limits for residues of metal catalysts or metal reagents;European Medicines Agency, Committee for Medicinal Products for Human Use,2008
4. An atomic spectroscopic method as an alternative to both USP heavy metal <231>and USP residue on ignition <281>. Stimuli to the revision process;Wang;USP Pharmacopeial Forum,2003
5. Changes to USP general chapter heavy metals <231>;Geary;Stimuli to the revision process. USP Pharmacopeial Forum,2004