Gordon, Raymond G., Jr. (ed.), 2005. Ethnologue: Languages of the World, Fifteenth edition. Dallas, Tex.: SIL International. Online version: http://www.ethnologue.com/.
Pittayaporn, Pittayawat, 2007. Tai dialects of Northern Vietnam: Sapa , Vinh Yen, and Cao Bang (Kra-Dai).
