<http://schema.org/alternativeHeadline>
"Three years later, Facebook is bringing back its F8 developer conference to San Francisco on April 30"^^<http://www.w3.org/2001/XMLSchema#string>
<http://thenextweb.com/facebook/2014/03/08/three-years-later-facebook-bringing-back-f8-developer-conference-april-30/>