The title is a book by Jonathan Porter Berkey, published by Cambridge University Press, 2003. In the book, there is a note about the unity of the Islamic world. The following is a review of the book and the note.
Review of the book
Jonathan Berkey surveys the religious history of the peoples of the Near East from approximately 600 to 1800 c.e. After examining the religious scene in the Near East in late antiquity, he investigates Islam's first century, the "classical" period from the accession of the Abbasids to the rise of the Buyid amirs. He then traces the emergence of new forms of Islam in the middle period, deftly showing how Islam emerged slowly as part of a prolonged process.
"Unity of the Islamic world" in the book
This was more 4 On the unity of the Islamic world, at least in southwest Asia and the Mediterranean regions, see S. D. Goitein, “ The Unity of the Mediterranean World in the Middle ' Middle Ages, ” in Studies in Islamic History and ...