A. C. Bent, 1942, _U. S. Natl. Mus. Bull._ 179, p. 490 (purple
martin). A. Wetmore and F. C. Lincoln, 1933, _Proc. U. S. Nat.
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Bannerman, 1933, _Birds of Tropical West Africa_, Vol. 3, p.
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swallows). W. H. Hudson, 1920, _Birds of La Plata_, Vol. 2, p.
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