Güldemann, Tom (2018). „Historical linguistics and genealogical language classification in Africa”. Ур.: Güldemann, Tom. The Languages and Linguistics of Africa. The World of Linguistics series. 11. Berlin: De Gruyter Mouton. стр. 299—308. ISBN978-3-11-042606-9. S2CID133888593. doi:10.1515/9783110421668-002.
Güldemann, Tom (2018). „Historical linguistics and genealogical language classification in Africa”. Ур.: Güldemann, Tom. The Languages and Linguistics of Africa. The World of Linguistics series. 11. Berlin: De Gruyter Mouton. стр. 299—308. ISBN978-3-11-042606-9. S2CID133888593. doi:10.1515/9783110421668-002.