"It's really important that we change our mindset from dependence on one source of energy to many different complementary sources, " Evans said.

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Selling branded toys and merchandise based on its very popular titles could open up an additional source of revenue, and help Zynga reduce its dependence on Facebook.

FORBES: Zynga Hooks Up With Hasbro To Make Money In Toys

In fact, over the past three years Deutsche Bank has deliberately and dramatically reduced its dependence on risk-taking as a source of operating earnings, while enjoying more substantial progress with clients than at any time in its recent history.

ECONOMIST: Russia's rotten statelets

Tourism is creating other problems for the local environment, too, including increased population density, over-dependence on wood as a fuel and construction source and the overgrazing and cutting of mountain slopes to feed livestock.

BBC: Everest's growing problem

Impressed by arguments that nuclear energy is a proven source of low-carbon power, and worried about the dependence on foreign fossil fuels caused by the decline of North Sea oil and gas, the government has been preparing the ground for a nuclear revival.

ECONOMIST: Nuclear power draws nearer as renewables retreat

With or without this Congress, I'm going to continue to do whatever I can to develop every source of American energy -- to make sure that three years from now our dependence on foreign oil is even lower, to make sure that our future is not controlled by events on the other side of the world.

WHITEHOUSE: President Obama Speaks on American Energy