old-north.co.uk/wordpress - history, language, and literature of yr Hen Ogledd (the Old North).
www.omniglot.com/writing/cumbric.htm - Information on Cumbric, and the constructed language Cumbraek based off it.
omniglot.com/language/numbers/celtic2.htm - Traditional ways of counting sheep in parts of north England, thought to be a remnant from Cumbric or some other Brittonic language.
en.wikipedia.org/wiki/Yan_tan_tethera - More on the traditional ways of sheep-counting.
Language in Pictland, by Forsyth (1997)
The Brittonic Language in the Old North A Guide to the Place-Name Evidence Volume 2, by James (2024)
A linguistic analysis of the river-names of two English counties, by Hardy (2022)
P-Celtic in Southern Scotland and Cumbria a review of the place-name evidence for possible Pictish phonology, by James (2013
The Problem of TH in Northern Brittonic Place-Names, by Whalley (2021)