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Description: |
xvii, 256 pages : illustrations ; 28 cm |
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Dissertation Note: |
Ph. D. Pennsylvannia State University 1989 |
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Bibliography Note: |
Includes bibliographical references. |
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Contents Note: |
Contents: 1. Introduction -- 2. Study areas and methods -- 3. Results -- 4. Discussion -- 5. Conclusion -- Appendices. |