Gabriele Sommer, 'A Survey on Language Death in Africa', in Brenzinger (2012) Language Death, p. 351.
Bkz. Hammarström, Harald; Forkel, Robert; Haspelmath, Martin, eds. (2017). "Hamba 16 Ekim 2021 tarihinde Wayback Machine sitesinde arşivlendi." Glottolog 3.0 Jena, Germany: Max Planck Institute for the Science of Human History.)
Hammarström, Harald; Forkel, Robert; Haspelmath, Martin, eds. (2017). "Okwa 15 Ekim 2021 tarihinde Wayback Machine sitesinde arşivlendi.". Glottolog 3.0. Jena, Germany: Max Planck Institute for the Science of Human History.
Gabriele Sommer, 'A Survey on Language Death in Africa', in Brenzinger (2012) Language Death, p. 351.
Bkz. Hammarström, Harald; Forkel, Robert; Haspelmath, Martin, eds. (2017). "Hamba 16 Ekim 2021 tarihinde Wayback Machine sitesinde arşivlendi." Glottolog 3.0 Jena, Germany: Max Planck Institute for the Science of Human History.)
Hammarström, Harald; Forkel, Robert; Haspelmath, Martin, eds. (2017). "Okwa 15 Ekim 2021 tarihinde Wayback Machine sitesinde arşivlendi.". Glottolog 3.0. Jena, Germany: Max Planck Institute for the Science of Human History.