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Africa ( ch. 7 ) . Gerrit J. Dimmendaal and F. K. Erhard Voeltz (2007) · In Encyclopedia of the World's Endangered Languages edited by Christopher Moseley · Routledge

Atlas of the World’s Languages in Danger . Christopher Moseley (ed.) (2010) · UNESCO Publishing http://www.unesco.org/culture/en/endangeredlanguages/atlas

Ethnologue: Languages of the World, 16th Edition (2009) . (2009) · edited by M. Paul Lewis · SIL International http://www.ethnologue.com/

Les bali et les peuplades apparentées: ndaka, mbo, beke, lika, budu, nyari ( pp. ix, 130, map ) . Geluwe, H. van (1959) · Ethnographic survey of Africa, Congo, #5; Annales du MRCB (Musée Royal du Congo Belge): monographies ethnographiques, #5 · Oxford Univ. Press