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, Volume 11. Berlin: De Mouton Gruyter. pp. 58–444, here 311. doi:10.1515/9783110421668-002. ISBN9783110421668. S2CID133888593.
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, Volume 11. Berlin: De Mouton Gruyter. pp. 58–444, here 311. doi:10.1515/9783110421668-002. ISBN9783110421668. S2CID133888593.