1. Thucydides, The Peloponnsian War, Book II, Chapter 77, translated by Rev. Henry Dale (London: Henry G. Bohn: 1851): pp. 1, 138–9.
2. Amos A. Fries and Clarence J. West, Chemical Warfare (New York: McGraw-Hill: 1921): p. 1.
3. Joseph Needham, Science and Civilisation in China, Vol. 5, Part 7: Military Technology: The Gunpowder Epic (New York: Cambridge University Press: 1986): p. 2.
4. Joseph Needham and Robin D. S. Yates, Science and Civilisation in China, Vol. 5, Part 6, Military Technology: Missiles and Sieges (Cambridge, UK: Cambridge University Press: 1994): pp. 470–471.
5. ibid.