Gippert, Jost (2018), chapter Sound Systems in Diachrony: Sibilants and Affricates in Udi, in Beyer, Klaus; Boden, Gertrud; Köhler, Bernhard; Zoch, Ulrike (Hrsg.), editors, Linguistics across Africa[1], Köln: Rüdiger Köppe, pages 113–132