Gerard, J. (1889). Science and Scientists: Some Papers on Natural History: No. IV. "Behold the Birds of the Air.". London.
Chicago-referens (17:e uppl.)Gerard, John. Science and Scientists: Some Papers on Natural History: No. IV. "Behold the Birds of the Air.". London, 1889.
MLA-referens (8:e uppl.)Gerard, John. Science and Scientists: Some Papers on Natural History: No. IV. "Behold the Birds of the Air.". London, 1889.
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