Kings (And Queens) Of The World: Where Monarchies Still Exist
"The British royal family never seems to lack attention from the press - witness the hype surrounding the marriage of Prince William, second in line to the throne, and Kate Middleton."
Meet the world's other 25 royal families
"With all the attention around Britain's forthcoming Royal Baby, you'd think the U.K. had a monopoly on monarchs -- infant or otherwise."
CIA World Factbook: Government Type
The International Commission and Association on Nobility
The Queen and the Commonwealth