If you want to see a poorly designed study, and one that seems to argue against providing UVB, check out Bradwell, Jordan, and Jessica Hackett (cited by Cosquieri). "The Effects of Ultraviolet (UV) Light Exposure on the Physiology And Behaviour of Captive Corn Snakes (Elaphe guttata)." RATEL (2013): 9. here.
Damn, that one is brutal. My inner scientist cringed so hard I couldn't get more than a few paragraphs in...