E. Peyer, Sorbian, Scottish Gaelic and Romansh: the Viability of Three Indigenous European Minority Languages, Liz., University of Fribourg, 2004, p. 62 ([Internet, 2018-08-16](https://doc.rero.ch/record/7816/files/Sorbian_Scottish_Gaelic_and_Romansh_-_the_Viability_of_Three_Indigenous_European_Minority_Languages.pdf))