1. Haug, W. (2009). Ethnic, religious and language groups: Towards a set of rules for data collection and statistical analysis. New York: Open Society Institute.
2. Lightfoot, D. (2006). How new languages emerge. Cambridge, UK: Cambridge University Press. See Chapter 8.
3. Verdoodt, A. F. (1998). The demography of language. In F. Coulmas (Ed.), Handbook of sociolinguistics (pp. 33–43). Oxford: Blackwell Publishing.
4. American Anthropological Association. (2014, March–April). Anthropology News 55(3).
5. Espenshade, T. J., & Fu, H. (1997). An analysis of English language proficiency among U.S. immigrants. American Sociological Review, 62, 288–305.