1. Reptile and amphibian variants—colors, patterns, and scales;Bechtel,1995
2. BSAVA manual of reptiles,2004
3. Axial bifurcation in serpents: an historical survey of serpent monsters having part of the axial skeleton duplicated;Cunningham,1937
4. Biomedical and surgical aspects of captive reptile husbandry;Frye,1991