Güldemann, Tom (2018). "Historical linguistics and genealogical language classification in Africa". In Güldemann, Tom (ed.). The Languages and Linguistics of Africa. The World of Linguistics series. Vol. 11. Berlin: De Gruyter Mouton. pp. 58–444. doi:10.1515/9783110421668-002. ISBN978-3-11-042606-9. S2CID133888593.
Hayward 2003, p. 246. Hayward, Richard J. (2003). "Omotic: the 'empty quarter' of Afroasiatic linguistics". In Jacqueline Lecarme (ed.). Research in Afroasiatic Grammar II: selected papers from the fifth conference on Afroasiatic languages, Paris 2000. Amsterdam: John Benjamins. pp. 241–261. doi:10.1075/cilt.241.13hay.
Güldemann, Tom (2018). "Historical linguistics and genealogical language classification in Africa". In Güldemann, Tom (ed.). The Languages and Linguistics of Africa. The World of Linguistics series. Vol. 11. Berlin: De Gruyter Mouton. pp. 58–444. doi:10.1515/9783110421668-002. ISBN978-3-11-042606-9. S2CID133888593.
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Rolf Theil (2006) Is Omotic Afro-Asiatic?Archived 2021-02-24 at the Wayback Machine pp 1–2: "I claim to show that no convincing arguments have been presented [for the inclusion of Omotic (OM) in Afro-Asiatic (AA)], and that OM should be regarded as an independent language family. No closer genetic relations have been demonstrated between OM and AA than between OM and any other language family."
Rolf Theil (2006) Is Omotic Afro-Asiatic?Archived 2021-02-24 at the Wayback Machine pp 1–2: "I claim to show that no convincing arguments have been presented [for the inclusion of Omotic (OM) in Afro-Asiatic (AA)], and that OM should be regarded as an independent language family. No closer genetic relations have been demonstrated between OM and AA than between OM and any other language family."