Analysis of information sources in references of the Wikipedia article "ISO 639-2" in English language version.
.Likewise, elements other than collections listed in ISO 639-2 are a subset of those listed ISO 639-3; each non-collective element in ISO 639-2 is included in ISO 639-3, but not necessarily vice versa. ... The language code in this part of ISO 639 does not include collective language code elements.