1. R.G. Gordon Jr. (ed): Ethnologue: Languages of the World, 15th edn. (SIL International, Dallas 2005), online version: http://www.ethnologue.com
2. Language Line Services, http://www.languageline.com
3. A.G. Chejne: The Arabic Language Its Role in History (University of Minnesota Press, Minneapolis 1969)
4. N. Haeri: Sacred Language Ordinary People: Dilemmas of Culture and Politics in Egypt (Palgrave MacMillan, New York 2003)
5. C.P. Masica: The Indo-Aryan Languages (Cambridge Univ. Press, Cambridge 1991)