Stats and info on the pros and cons of spaying and neutering

I'm looking for articles, and studies, with cited info about who wrote/paid for/etc. the studies, on health problems in fixed dogs VS. unfixed dogs.

Stuff like higher rates of hypothyrodism and sarcomas in fixed dogs, other cancers in unfixed dogs, anything along those lines.

AVMA - Journal of the American Veterinary Medical Association - 231(11):1665 - Citation (link to the full text at the bottom of the page)