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3. J. H. Zar Biostatistical Analysis (Prentice-Hall Upper Saddle River NJ 1996).
4. D. W. Lowe J. R. Matthews C. J. Moseley The Official World Wildlife Fund Guide to Endangered Species of North America vols. 1 and 2 (Walton Beacham Washington DC 1990).
5. C. J. Moseley The Official World Wildlife Fund Guide to Endangered Species of North America vol. 3 (Walton Beacham Washington DC 1992).