1. Schmidt, Stephen R. and Robert G. Launsby. Understanding Industrial Designed Experiments (4th Edition), p. 1. 7, Air Academy Press, Colorado Springs, CO (1994).
2. Deming, W. Edwards. Out of the Crisis, p. 465, MIT Center for Advanced Engineering Study, Cambridge, MA (1986).
3. British Deming Association (BDA). The Role of the Coordinator (#5), p. 12, SPC Press, Inc., Knoxville, TN (1992).
4. British Deming Association. A System of Profound Knowledge (#9), pp. 12–13, SPC Press, Inc., Knoxville, TN (1992).
5. British Deming Association. Profound Knowledge (#6), p. 2, SPC Press, Inc., Knoxville, TN (1992).