Editing Metric system (section)

===Extensibility===
The metric system is extensible since the governing body reviews, modifies and extends it needs arise. For example, the [[katal]], a derived unit for catalytic activity equivalent to one [[mole (unit)|mole]] per second (1&nbsp;mol/s), was added in 1999.<ref>{{Cite journal |last=Dybkær |first=René |date=2002-03-01 |title=The Tortuous Road to the Adoption of katal for the Expression of Catalytic Activity by the General Conference on Weights and Measures |journal=Clinical Chemistry |volume=48 |issue=3 |pages=586–590 |doi=10.1093/clinchem/48.3.586 |issn=0009-9147 |pmid=11861460|doi-access=free }}</ref>