Crystal, David (2003a). English as a Global Language, 2nd, Cambridge University Press, გვ. 6. ISBN978-0-521-53032-3. ციტირების თარიღი: 4 February 2015. „The statistics collected in chapter 2 suggest that about a quarter of the world's population is already fluent or competent in English, and this figure is steadily growing—in the early 2000s that means around 1.5 billion people.“