ISO 639-2

ISO 639-2:1998, Codes for the representation of names of languages — Part 2: Alpha-3 code, is the second part of the ISO 639 standard, which lists codes for the representation of the names of languages. The three-letter codes given for each language in this part of the standard are referred to as "Alpha-3" codes. There are 464 entries in the list of ISO 639-2 codes.
Applicable codes in this context include
Special codes in ISO 639-2:
*und undetermined (language) 
*mis uncoded language 
*mul multiple languages 
*zxx no linguistic content, not applicable 
More information and a full list of language codes on the Wikipedia page . The Library of Congress page is . There are various other web pages on the topic.
Category:Reference
Category:20th century