The most common source of thorium is the rare earth phosphate mineral, monazite.

FORBES: Is Thorium the Biggest Energy Breakthrough Since Fire? Possibly.

In 2006, two-fifths or 40% of all working mothers relied on informal childcare, with grandparents being the most common source for a third of parents.

BBC: 'End of nuclear family' forecast

Nearly 30% of the companies that listed in the U.S. came from other parts of the world, and China was the most common source of foreign listings.

WSJ: IPO Activity Picked Up in 2010

Personally, I just think that solar makes the most sense as an energy technology, and the tech innovations in solar power are such that I expect it to be the most common source of power before the century is out.

FORBES: The Cost of Solar Power Is Expected to Decline 50% Over the Next Decade

To put that figure in context, Iannelli says that the energy required to pump freshwater from underground (which, he says, is the most common source of drinking water in the West) typically produces just over 1.5 tonnes of CO2 per million gallons.

CNN: Counting the carbon cost of bringing water to the desert

Cruise lines quickly blame the passengers for not washing their hands, but the CDC and the Food and Drug Administration concluded long ago that the most likely and common source of norovirus is contaminated food or water.

CNN: What cruise lines don't want you to know

The most common accusation is that Tyco used thousands of acquisitions to play accounting tricks that became the source of the firm's earnings growth.

ECONOMIST: Tyco: Not guilty, your honour | The