Derived from the sourced literature on The Reptile Database: Burbrink and Guiher (2014), Considering gene flow when using coalescent methods to delimit lineages of North American pitvipers of the genus Agkistrodon. Zoological Journal of the Linnean Society, 173: 505-526. doi:10.1111/zoj.12211 (http://cnah.org/pdf/88290.pdf).

See related flags:
https://www.inaturalist.org/flags/251295
https://www.inaturalist.org/flags/383267