↑Say, T. (1823) In James, E. Account of an expedition from Pittsburgh to the Rocky Mountains, performed in the years 1819, '20, by order of the Hon. J. C. Calhoun, Secretary of War, under the command of Major Stephen H. Long. Vol. 2., Philadelphia, H. C. Carey & I. Lea.
↑Baird, S. F. and C. Girard. (1853) Catalogue of North American Reptiles in the Museum of the Smithsonian Institution. Part 1.-Serpents., Smithsonian Inst., Washington, xvi + 172 pp.
↑ 4.04.1Bisby F.A., Roskov Y.R., Orrell T.M., Nicolson D., Paglinawan L.E., Bailly N., Kirk P.M., Bourgoin T., Baillargeon G., Ouvrard D. (ed.) (2011). "Species 2000 & ITIS Catalogue of Life: 2011 Annual Checklist". Species 2000: Reading, UK. Ginkuhà 24 Septyembre 2012.CS1 maint: multiple names: authors list (link) CS1 maint: extra text: authors list (link)
