Breitbarth, Anne, Christopher Lucas & David Willis, eds. 2011. The Development of Negation: The languages of Europe and the Mediterranean. 21 vols. Oxford: Oxford University Press.
Larrivée, Pierre & Ingham Richard, eds. 2011. The Evolution of Negation: Beyond the Jespersen Cycle. Berlin: Mouton de Gruyter.
Roberts, Ian & Anna Roussou. 2003. Syntactic Change: A minimalist approach to grammaticalization. Cambridge: Cambridge University Press.