Measurement unit is a controlled vocabulary listing units of measurement with their authority codes. If available, the codes are based on the code list recommendation N°. 20 "Codes for Units of Measure Used in International Trade" (as revised periodically) maintained and published by UNECE through its Center for Trade Facilitation and Electronic Business (UN/CEFACT). It is maintained by the Publications Office of the European Union and disseminated on the EU Vocabularies website.