Excerpt from change request document:

Wumeng and Wusa have long been recognized as distinct varieties of Nasu, but Wumeng is spoken primarily in Guizhou Province with some speakers also living in Yunnan Province (thus matching the [ywu] profile), and Wusa is spoken only in Guizhou Province (thus matching the [yig] profile). The Ethnologue profile associated with [ywm], however, claims that the language is spoken only in Yunnan. The confusion, then, can likely be traced back to a lack of understanding regarding a single variety spoken on both sides of a provincial line. Thus, [ywm] should be merged into [ywu], the [ywu] reference name should be changed to reflect the Wumeng distinction, and the [yig] reference name should be changed to reflect the Wusa distinction (cf. the related [ywu] and [yig] reference name change applications).