Usefull links
Weights and Measures:
http://ts.nist.gov/WeightsAndMeasures/Metric/upload/EUMetricDirective2010.pdf
http://www.asd-stan.org/sales/asdocs.asp
SI Unit rules and style conventions, National Institute of Standards and Technology (NIST), [Docket No. 980430113-8113-01]