<http://schema.org/description>
"As we reported earlier, Twitter has published new figures showing that it now has 145 million registered users. The thing is, that doesn't really tell us much about how many people ..."^^<http://www.w3.org/2001/XMLSchema#string>
<http://thenextweb.com/socialmedia/2010/09/03/how-many-people-are-actually-using-twitter/>