FUENTE: “A rapid appraisal survey of the Abo and Barombi speech communities, South West and Littoral Provinces, Cameroon” (28) . Lamberty, Melinda (2002) SIL International

FUENTE: “The World Atlas of Language Structures” . , Bernard Comrie and David Gil and Martin Haspelmath and Matthew S. Dryer · Oxford University Press

FUENTE: “Ethnologue: Languages of the World, 16th Edition (2009)” . , M. Paul Lewis · SIL International