Kirill Babaev, « Joseph Greenberg and the Current State of Niger-Congo », Journal of the Association for the Study of Language in Prehistory, (lire en ligne)
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(en) Gerrit Jan Dimmendaal, Historical Linguistics and the Comparative Study of African Languages, Amsterdam/Philadelphia, John Benjamins Publishing, , 421 p. (ISBN978-90-272-1178-1 et 90-272-1178-7, lire en ligne)