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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.