For such averages within Canaan, refer to Sir Harry Luke, Traveller’s Handbook for Palestine and Syria (London: Simpkin, Marshall, Hamilton & Kent, 1924), pp. 206, 275–279. For the same averages in Mesopotamia, consult Alois Musil, The Middle Euphrates, a topographical itinerary, (New York: American Geographical Society, 1927), p. 200.