LGC Promochem ^*

http://www.lgcpromochem.com/

National Institutue of Standards and Technology (NIST)^*

NIST supplies industry, academia, government, and other users with over 1100 reference materials of the highest quality and metrological value.

http://www.nist.gov/

The sole officially recognised Certificated Reference Material produced from China
http://inms-ienm.nrc-cnrc.gc.ca/

Providing Certified Reference Materials and QA services for water and sediment trace elements.

http://www.nwri.ca/