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Campbell JA, Lamar WW (2004). The Venomous Reptiles of the Western Hemisphere. 2 volumes. Ithaca and London: Comstock Publishing Associates. 870 pp., 1500 plates. ISBN0-8014-4141-2.
Behler JL, King FW (1979). The Audubon Society Field Guide to North American Reptiles and Amphibians. New York: Alfred A. Knopf. 743 pp. LCCCN 79-2217. ISBN0-394-50824-6. (Crotalus viridis helleri, pp. 694–695 + Plate 627).