The Mountain West Digital Library Dublin Core Application Profile, Version 2.0 (20 July 2011) stipulates the use of ISO 639-3 three letter codes. ISO 639-3 Codes for the representation of names of languages, part 3 is a code that aims to define three-letter identifiers for all known human languages. At the core of ISO 639-3 are the individual languages already accounted for in ISO 639-2. See the List of terms.
en-US (English as used in the United States)
Primary Language Subtag
US (United States)
en-GB (English - United Kingdom)
en-NZ (English - New Zealand)
en-CA (English - Canada)