<http://schema.org/mainEntityOfPage>
<http://www.upi.com/Sports_News/2013/02/20/Serena-Williams-out-with-back-injury/25421361385339/>
<http://www.upi.com/Sports_News/2013/02/20/Serena-Williams-out-with-back-injury/UPI-25421361385339/?rel=68611361645173>