<http://schema.org/about>
"On April 22, 1970, 20 million people across America celebrated the first Earth Day. It was a time when cities were buried under their own smog and polluted rive"^^<http://www.w3.org/2001/XMLSchema#string>
<http://www.mnn.com/lifestyle/responsible-living/stories/earth-day-on-mnn>