Why it is so tough has always lacked a good explanation but now researchers at the University of Southern California's School of Dentistry are closing in on the secret.

BBC: By BBC News Online Science Editor Dr David Whitehouse

And that is why, when the stakes are so high, we can always trust this man.

WHITEHOUSE: Remarks by the First Lady at a Campaign Event

For me it was a nice personal kind of a journey, so I think maybe that is why Chris is saying I was always the one who said, 'Let's do that.

BBC: Newsbeat - Entertainment - More X-Files movies a possibility

There are always challenges in the wings that we have not seen, so that is why it's vitally important that we do this work and we work out exactly how many people we can employ.

BBC: Metropolitan Police faces ?500m 'cuts challenge'

My pastor always says no day is promised, so if that's the case, why do we engage in this counterproductive lowering of expectations?

CNN: Commentary: Obama's ambitious agenda a good thing