1. EPA-650/4-75-005;C. Buell,1975
2. David, F. N. 1938, Tables of the Ordinates and Probability Integral of the Distribution of the Correlation Coefficient in Small Samples, The Biometrika Office, Cambridge University Press, Cambridge, England.
3. Ezekiel, M.: 1941, Methods of Correlation Analysis, John Wiley and Sons, Inc., London, England.
4. Gether, J. and Seip, H.: 1979, ?Analysis of Air Pollution Data by the Combined Use of Interactive Graphic Presentation and a Clustering Technique?, Atmos. Environment 13, 87?96.
5. Gustafson, S. and Kortanek, K.: 1973, ?Determining Sampling Equipment Locations by Optimal Experimental Design with Application to Environmental Protection and Acoustics?, Math. in the Social Scienes, Paper 90?725.