<http://schema.org/about>
"With a daily ridership in excess of 5 million commuters, the New York City Subway system ranks among the world's most trafficked -- though there's another species making use of the facilities in a whole different way."^^<http://www.w3.org/2001/XMLSchema#string>
<http://www.treehugger.com/natural-sciences/new-york-subway-uses-nature-sounds-to-ward-off-pigeons.html>