H. Barth, Travels in North and Central Africa, Vol. I, pp. 202, 277-281. New York, 1857.
Ratzel, History of Mankind, Vol. III, p. 173. London, 1896-1898.
Ibid., Vol. III, Chapter on Islam, pp. 195-204.
George Adam Smith, Historical Geography of the Holy Land, pp. 28-30. New York, 1897. L. March Phillipps, In the Desert, pp. 101-105. London, 1905.
E.A. Freeman, Historical Geography of Europe, pp. 114-116. London, 1882.
George Adam Smith, Historical Geography of the Holy Land, pp. 88-90. New York, 1897.
Jeremiah, Chap. XXXV, 6-14.