Occasionally it will be hundreds of millions and once in a blue moon billions.

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And then, every once in a blue moon, something comes along that is in a category all its own.

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Once in a blue moon, he tells me, he saw an iPhone.

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Once in a blue moon, we might have no other explanation than that it was a perfect storm of random events, such as technological breakthroughs or social transitions.

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Maybe it's time (once in a blue moon) for a high-level bipartisan commission--televised and transparent--to review the science, the costs and the regulatory processes, taking into account the national interest.

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Director of the Medical Research Council's clinical sciences centre Chris Higgins said "Once in a blue moon something does not get picked up in animals which is there in man".

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Such things happen once in a blue moon.

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