U.S. Soil Survey Staff. Soil Survey Manual, U.S. Government 

 Printing Office, Washington, D.C., 1951. 



Weaver, J. E., and F. E. Clements. Plant Ecology, 2nd Edi- 

 tion, McGraw-Hill Book Co., Inc., New York, N. Y., 1938. 



Welch, Paul S. Limnology, McGraw-Hill Book Co., Inc., 

 New York, N. Y., 1935. 



Woodbury, A. M. Principles of General Ecology, McGraw- 

 Hill Book Co., Inc. New York, N. Y., 1954. 



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