I don't know if this has been mentioned here or not, but
http://spankingart.wikia.com
It's an online encyclopedia about everything and anything related to spanking including entries on famous individuals in the scene, techniques, positions, uniforms, implements, pretty much every aspect of the spanking kink analyzed in excruciating detail. It's real scholarly and stuff.
I myself have joined in the fun by posting a couple of articles, and am working on a third.
So it's your one-stop shop if you need to do some research on the spanking phenomenom for your thesis.