1. Carnegie-Mellon University, Social Studies Center, The Shaping of Western Society (Public Domain Edition available from General Systems and Graphics, Inc., 933 Penn Avenue, Pittsburgh, Pa. 15222: 1966), pp. 269–274.
2. The New Social Studies
3. Habberton, William, Roth, Lawrence V. and Spears, William R., World History: The Story of Man’s Achievement (River Forest, Laidlaw Brothers, 1962), pp. 343–346; and Manual, Tests, Answers for World History, p. 73.