Bismark, Christina. 2011. Shared alternatives to subject-verb agreement: the third singular verb and its uses in English and Brittonic, thèse, pdf.
Introduction: "The Standard English (StE) verbal paradigm of the present tense indicative displays person-number marking on one of its members, namely the 3rd person singular. In non-standard varieties of English, on the other hand, the use of the 3rd singular -s form is neither limited to this specific member of the paradigm, nor is it restricted to the function of person-number marking. Instead its use is conditioned by a wide range of other factors resulting in a variety of different verbal paradigms. One such factor is the type of the subject accompanying the verb. Where it is a full noun, verbal -s is used with 3rd person singular as well as with 3rd person plural verbs. This linguistic constellation, in which the form of the verb is conditioned by the nature of its subject, is rare in the languages of the world. Yet, it is also inherent in the Brittonic languages Welsh, Breton and Cornish and in the Goidelic language family. The motivation for the present study was provided by the parallel occurrence of this rather uncommon feature in genetically unrelated but closely adjoining languages and the doubts voiced in previous research about a possible diffusion of the feature between the languages. Its basic objective is to take stock of the large group of non-standard verbal -s phenomena which the shared feature stems from, in an attempt to elicit further parallels. In doing so, I hope to define the nature and to foster the concept of a relation between English and Brittonic. The originality of this study will be illustrated against the background of previous research on individual aspects of the present topic."