Jadranka Gvozdanović (1999). Numeral Types and Changes Worldwide. Walter de Gruyter. m/s. 221. ISBN978-3-11-016113-7.: "The usage of 'Aryan languages' is not to be equated with Indo-Aryan languages, rather Indo-Iranic languages of which Indo-Aryan is a subgrouping."
Hammarström, Harald; Forkel, Robert; Haspelmath, Martin, penyunting (2017). "Indo-Iranian". Glottolog 3.0. Jena, Germany: Max Planck Institute for the Science of Human History.
washingtonpost.com
Noack, Rick. "The future of language". Washington Post (dalam bahasa Inggeris). Dicapai pada 2020-03-27.