- McWhorter, J. H. 2009. 'What else happened to English? A brief for the Celtic hypothesis', English Language and Linguistics 13 (02), 163-191.
Abstract: "This article argues that despite traditional skepticism among most specialists on the history of English that Brythonic Celtic languages could have had any significant structural impact on English's evolution, the source of periphrastic do in Cornish's equivalent construction is virtually impossible to deny on the basis of a wide range of evidence. That Welsh and Cornish borrowed the construction from English is impossible given its presence in Breton, whose speakers left Britain in the fifth century. The paucity of Celtic loanwords in English is paralleled by equivalent paucity in undisputed contact cases such as Uralic's on Russian. Traditional language-internal accounts suffer from a degree of ad hocness. Finally, periphrastic do is much rarer cross-linguistically than typically acknowledged, which lends further support to a contact account."