The U.S. has major reserves of the vital minerals, but a combination of tough environmental rules and lowball Chinese pricing drove the main domestic producer out of business.

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One solution would be to import doctors from other countries, but a combination of tight licensing rules and a limited number of residency slots holds down their numbers.

FORBES: Heads Up

Deloitte says a combination of fair play rules and straitened economic times, which are limiting revenue growth, may see a majority of top flight clubs reporting operating losses rather than profits.

BBC: Premier League club wages climb to new highs

With ever-stricter environmental laws in combination with state-set green energy rules, the value of biomass facilities is expected to rise.

FORBES: Biomass Breathing New Life Into Coal Plants

Unless the SEC and Financial Industry Regulatory Authority craft strong rules, Mr. Abshure said, a combination of fraud, high failure rates for startups and an "inevitable advertising onslaught of pie-in-the-sky offers" will kill investor confidence in buying shares online.

WSJ: Crowdfunding Efforts Draw Suspicion

EU's institutions and rules, in the hope of achieving the elusive combination of simultaneously deepening and widening the Union.

ECONOMIST: Europe's mid-life crisis

The second is the ability to combine words according to rules in such a way that the meaning of the combination is predictable from the meanings of the words and the way they are arranged.

FORBES: Magazine Article

They can influence it through choice of rules regarding eligibility, scoring, and fouls (to some extent), but the final combination on display on NBA courts mixes these choices with the unintended consequences of them along with team methods and with the long run evolution of player skills.

FORBES: NBA Centers Face Extinction