Braj Kachru's Three Circles of English.
English is the native mother-tongue of only Britain, Ireland, USA, Canada, Australia, New Zealand and a handful of Caribbean countries. But in 57 countries (including Ghana, Nigeria, Uganda, South Africa, India, Pakistan, Singapore, Philippines, Fiji, Vanuatu, etc), English is either as its “official language” or a majority of its inhabitants speak it as a first language. These are largely ex-colonial countries which have thoroughly integrated English into its chief institutions.