Seventeen years later, supporters still call the ERA an essential constitutional principle.

CNN: A new version of the ERA

This "control principle" was essential to the relationship between the UK and the US, he told MPs.

BBC: Torture papers statement

The S3-BT speakers are based on an essential, time-honored principle: good sound depends on intelligent design and superior materials.

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The state plays an essential role as defender of this principle, setting standards and norms that guarantee quality and equality of opportunity.

UNESCO: MEDIA SERVICES

How that will happen and under what financial terms are essential to iron out at least in principle before starting the business.

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