President Obama even made a light-hearted reference to Mr Netanyahu's warning of a "red line" with Iran's nuclear programme.

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An audience member shouted out "Doc" perhaps a light-hearted reference to Sherlock Holmes's sidekick.

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The gift was a light-hearted reference to US Vice-President Joe Biden's recent remark that the new US administration wanted to reset ties with Russia after years of friction.

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Now, perhaps, the memory of his life can serve as a light for others, as a point of reference on our horizons.

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In Dr Attari's study, for example, the survey provided a reference measure by stating the amount of energy used by a standard light bulb.

ECONOMIST: Energy conservation

Comprised of a surface pattern of triangles-like those in the main theater, but made in this case out of 1, 067 thin aluminum panels, mounted on the support structure with open joints-the light-blue facade looks razor-sharp but creates the impression of a super-light floating skin dematerialized against the sky: another visual reference in the architecture to the infinite thinness of the moving image.

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And that geometrical prediction was confirmed directly by the Sloan survey, using the known distances of 500m light years to the density peak and 13 billion light years to the region where the microwave background originates as reference points to look for geometrical distortion, in the way that a more traditional land survey might use triangulation points.

ECONOMIST: Astronomy

Usually, this is said in reference to the rise of LEDs, of the technologies driving ever-more-efficient light.

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