Is there a theorist who discussed World English?

Whilst most students will refer to Kachru's 'Circles' model. Another useful theorist to remember is Schneider, who proposed the dynamic model. Schneider studied how English becomes established around the world. There are five hypothesised stages in the model: foundation, exonormative stabilisation (looking to L1 countries for standards and norms), nativization (phonology and syntax becomes tied more closely to native language), endonormative stabilisation (country looks inwards for standards and norms) and differentiation (regional varieties develop). It could be argued that Dutch English is at stage 2, Ghanaian English is at stage 3 and Hinglish is stage 5.