Gutzke, William H. N.; Packard, Gary C. (Jan–Feb 1987). "Influence of the Hydric and Thermal Environments on Eggs and Hatchlings of Bull Snakes Pituophis melanoleucus". Physiological Zoology. 60 (1): 9–17. doi:10.1086/physzool.60.1.30158624. ISSN0031-935X. S2CID87772315.
Gutzke, William H. N.; Packard, Gary C. (Jan–Feb 1987). "Influence of the Hydric and Thermal Environments on Eggs and Hatchlings of Bull Snakes Pituophis melanoleucus". Physiological Zoology. 60 (1): 9–17. doi:10.1086/physzool.60.1.30158624. ISSN0031-935X. S2CID87772315.
Gutzke, William H. N.; Packard, Gary C. (Jan–Feb 1987). "Influence of the Hydric and Thermal Environments on Eggs and Hatchlings of Bull Snakes Pituophis melanoleucus". Physiological Zoology. 60 (1): 9–17. doi:10.1086/physzool.60.1.30158624. ISSN0031-935X. S2CID87772315.