<http://schema.org/about>
"The average age of visitors has skyrocketed over the past few decades, and some fear the future of these national treasures could be in jeopardy."^^<http://www.w3.org/2001/XMLSchema#string>
<http://www.mnn.com/earth-matters/wilderness-resources/videos/at-national-parks-where-are-all-the-young-people>