Here are some links that you should find helpful, some also contain additional links.
"White Space information from Shure":
http://www.shure.com/proaudio/pressroom ... /index.htm
The FCC's information on 700MHz Public Safety band:
http://www.fcc.gov/pshs/public-safety-s ... yband.html
A good summary from Sweetwater:
http://www.sweetwater.com/feature/wirel ... spaces.php
Whitespace information from ElectroVoice:
http://www.electrovoice.com/pressreleases/880.html
Those are some of the better ones. If you want more information try googling "Wireless Microphone White Space" or "700 Mhz Band" you'll get a bunch more info.