L. Kruckenhauser, E. Haring, W. Pinsker, M. J. Riesing, H. Winkler, M. Wink, A. Gamauf: Genetic vs. morphological differentiation of Old World buzzards (genus Buteo, Accipitridae). In: Zoologica Scripta. Band 33, Nr. 3, 2004, S. 197–211, doi:10.1111/j.0300-3256.2004.00147.x.