1. The Balloon Rules for a Rough Estimate of the Correlation Coefficient
2. Hoel, Paulg. 1971.Elementary Statistics,, 3rd ed., 192New York: John Wiley.
3. Meyer, Paul L. 1970.Introductory Probability and Statistical Applications,, 2nd ed., 299Reading, Mass.: Addison-Wesley.
4. Runyon, R. P. and Haber, A. 1984.Fundamentals of Behavioral Statistics,, 5th ed., 143Reading, Mass.: Addison-Wesley.
5. Geometry, Statistics, Probability: Variations on a Common Theme