1. Undaunted Courage: Meriwether Lewis, Thomas Jefferson, and the Opening of the American West;Ambrose,1997
2. Bates, H.W., 1863. The Naturalist on the River Amazons. Available in reprint versions from various publishers.
3. Belt, T., 1874. The Naturalist in Nicaragua. Available in modern reprints, such as the Leopold Classic Library, 344 pp.
4. The Voyage of the Beagle;Darwin,1839
5. Green Laurels: The Lives and Achievements of the Great Naturalists;Peattie,1936