Dr Nicola Galloway is one of the leading academics in the issues relevant to Global English. She has published two books in this field:

“Introducing Global Englishes”: https://www.routledge.com/Introducing-Global-Englishes/Galloway-Rose/p/book/9780415835329

“Global Englishes and Change in English language teaching”  https://www.routledge.com/Global-Englishes-and-Change-in-English-Language-Teaching-Attitudes-and/Galloway/p/book/9780415786201