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2. Archibald, G.W., 1976a. Crane taxonomy as revealed by the unison call. In: Lewis, J.C. (Ed.), Proceedings International Crane Workshop 1975. Oklahoma State University Publishing and Printing, Stillwater, pp. 225–251.
3. Archibald, G.W., 1976b. The Unison Call of Cranes as a Useful Taxonomic Tool. Ph.D. dissertation. Cornell University, Ithaca, New York.
4. Armstrong, E.A., 1963. A Study of Bird Song. Oxford University Press, London.
5. Bent, A.C., 1926. Life Histories of North American Marsh Birds. Bulletin 135, Smithsonian Institution, Washington, DC.