The trouble is that not much from that period survives and particularly not organic material, so we cannot be sure.

NPR: Looking at the World Through Beer Glasses

That is almost certainly true, even though we cannot be sure what form that test will take or from which quarter.

CENTERFORSECURITYPOLICY: Will Obama 'go to' defense?

"Until we find out what happened we cannot be sure that the second wheel will not suffer similar problems, " a spokeswoman said.

BBC: Cambridgeshire composter breakdown costs ?60,000 a week

If the US can increase production by 25% within the decade, could the world?? I doubt it, but we cannot be sure, because there are bound to be fields in other countries ripe for exploitation with the same technology.

FORBES: US Oil Industry Leads the Way in Extracting Hard-to-Get Crude; Steel to Benefit

"The initial set of indicators suggests wide variation in both practice and outcomes between maternity units which is a source of concern for the specialty as we cannot be sure that every woman is getting the best possible care, " he said.

BBC: Maternity care varies across England

Of course, we cannot be sure whether the 53% of deals which destroyed value were among organisations which would have lost value against competition if they had not merged but one of the sure-fire ways to stack the odds against yourself is to look at your target or partner from a business point of view only.

ECONOMIST: Letters

We cannot even be sure what our tax rates will be next year.

FORBES: Does Newton's First Law of Motion Apply to Recessions?

What I can say for sure, however, is this: We cannot afford to be in the dark and the cold for too long.

FORBES: Do Local Communities Need a New Business Model for Electric Utilities?