KORTMANN, Bernd; AUWERA, Johan van der. The Languages and Linguistics of Europe: A Comprehensive Guide. [s.l.]: Walter de Gruyter 934 s. Dostupné online. ISBN9783110220261. (anglicky) Google-Books-ID: vi_VCm51kpkC.
unesco.org
UNESCO Atlas of the World's Languages in danger. www.unesco.org [online]. [cit. 2019-07-29]. Dostupné online.