Elaine Tarone; Martha Bigelow; Kit Hansen (2013). Oxford Applied Linguistics: Literacy and Second Language Oracy. Oxford University Press. pp. 55, 73–74 with footnote 5. ISBN978-0-19-442313-7., Quote: "In addition to the Bantus, there are Somali clans considered to be of low caste and treated as outcasts. They are the Yibir, the Midgan and the Tumal. They face restrictions, prejudice, discrimination, harassment and attacks in East Africa as well as in the Diaspora."
Lewis, Herbert S. (2006). "Historical Problems in Ethiopia and the Horn of Africa". Annals of the New York Academy of Sciences. 96 (2). Wiley-Blackwell: 508–509. doi:10.1111/j.1749-6632.1962.tb50145.x. S2CID83677517.
Lewis, Herbert S. (2006). "Historical Problems in Ethiopia and the Horn of Africa". Annals of the New York Academy of Sciences. 96 (2). Wiley-Blackwell: 508–509. doi:10.1111/j.1749-6632.1962.tb50145.x. S2CID83677517.