Matasovic, Ranko (2007). "Insular Celtic as a Language Area". In Tristram, Hildegard L.C. (ed.). The Celtic Languages in Contact (Papers from the Workshop within the Framework of the XIII International Congress of Celtic Studies). Postdam University Press. p. 106. ISBN978-3-940793-07-2.
Adams, J. N. (2007). "Chapter V – Regionalisms in provincial texts: Gaul". The Regional Diversification of Latin 200 BC – AD 600. Cambridge. pp. 279–289. doi:10.1017/CBO9780511482977. ISBN9780511482977.{{cite book}}: CS1 maint: location missing publisher (link)
fordham.edu
Historia Francorum, i.30. Later local traditions inserted locally venerated bishops into this group, to establish parity with the seven churches of Gaul.
David Dalby, 1999/2000, The Linguasphere register of the world’s languages and speech communities. Observatoire Linguistique, Linguasphere Press. Volume 2. Oxford.[1]