1. Monographs on Soil and Resources;P. A. Burrough,1986
2. Chadwick, M. J. and Kuylenstierna, J. C. I.: 1990, The Relative Sensitivity of Ecosystems in Europe to Acidic Depositions, Stockholm Environment Institute, Stockholm, Sweden.
3. Clean Air Act: 1970, U.S. Government Printing Office, Washington, DC.
4. Clean Air Act Amendments: 1990, S. 1630. U.S. Government Printing Office, Washington, DC.
5. Cressie, Noel A. C.: 1991, Statistics for Spatial Data, John Wiley & Sons, Inc., New York, NY.