Wright AH, Wright AA (1957). Handbook of Snakes of the United States and Canada. Ithaca and London: Comstock Publishing Associates, a division of Cornell University Press. 1,105 pp. (in 2 volumes) (Hypsiglena torquata texana, pp. 326-330, Figure 101 + Map 30 on p. 315).
Mulcahy DG (2007). "Molecular systematics of neotropical cat-eyed snakes: a test of the monophyly of Leptodeirini (Colubridae: Dipsadinae) with implications for character evolution and biogeography". Biological Journal of the Linnean Society92: 483-500. (Hypsiglena jani).