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Distribution and field identification of Philippine birds of prey: 1. Philippine Hawk Eagle Spizaetus philippensis and Changeable Hawk Eagle Spizaetus cirrhatus
Methods of studying water relations, Bohdan Slavik, Ecological Studies Band 9, J. Jakob, O. Lange, JS Olson, W. Wieser (Eds.), Springer-Verlag, Berlin-Heidelberg-New York (1974), XIII, 449 S. und 181 Abbildungen. geb. DM 76