1. H.A.R. Gibb, Mohammedanism, 2nd ed. (London, New York: Oxford University Press, 1969) p.26, quoting Koran.
2. M.W. Watt, Islam and the Integration of Society (London: Routledge and Kegan Paul, 1961) p.42.
3. P.K. Hitti, Makers of Arab History (London: Macmillan, 1969), p.3.
4. P.K. Hitti, History of the Arabs, 10th ed. (London: Macmillan, 1973) p.353.
5. R. Levy, The Social Structure of Islam (London, New York: Cambridge University Press, 1957) p.195.