E16/E17 lists Buya [byy] as an Unclassified Southern Bantoid language of the DRC without a location. This must emanate from William E. Welmers 1971 :788-789 since that is the only source mentioning such a language with exactly that much (lack of) information. In all likelihood, Buya [byy] is a rendering of a DRC language already counted in another E16/E17 entry, presumbly Buyu [byi]. See also: Buyu [byi].
Retired in ISO 639-3: Retire