1. DTI 2003 http://www.dti.gov.uk/nms/
2. Concept of a National Measurement System;Huntoon;Science,1967
3. The National Measurement System-The Hidden Giant;Minck;NCSL Newsletter,1977
4. NIST 2003 http://www.nist.gov
5. NMLTaiwan 2003 http://www.nml.org.tw/en/NMS/nms_1.html