LGC Promochem ^*

LGC Promochem is Europe’s most comprehensive source of reference materials.

http://www.lgcpromochem.com/home/home_en.aspx

United States Pharmacopeia (USP) ^*

USP's official Reference Standards are highly characterized specimens of drug substances, excipients, impurities, degradation products, dietary supplements, compendial reagents and performance calibrators. They are required for use in conducting official USP–NF tests and assays.

http://www.usp.org/