<http://schema.org/description>
"Most of us are unaware of the fact that Gmail has an inbuilt UNDO option that helps a user to undo sent email messages easily."^^<http://www.w3.org/2001/XMLSchema#string>
<http://www.gizbot.com/how-to/tips-tricks/did-you-know-you-can-undo-sent-email-gmail-check-out-035216.html>