1. E.H.G. Dobby, Southeast Asia (London: University Press, 1966), p. 315.
2. Shannon McCune, The Diversity of Indochina’s Physical Geography, Far Eastern Quarterly, Vol. 6 (August, 1947), p. 337
3. Norton Ginsburg, editor, The Pattern of Asia (New Jersey: Prentice-Hall, Inc., 1958), p. 416.
4. Donald Fryer, Emerging Southeast Asia (New York: McGraw-Hill Book Company, 1970), p. 398.
5. Ginsburg, p. 420.