Some scientists suggest that this may not be an unprecedented event.

An unprecedented event, to be sure, but just another example of how the Administration's strategy in pursuing arms control has been the correct one.

The bigger question is: why did such an unprecedented event occur?

In the 100 days since then, the country has witnessed an unprecedented event.

The strike was described as "complete and entire, an unprecedented event outside the continental countries".

The condemnation of a scientific study by Congress was, at that time, an unprecedented event.

It would cause the government to default on its legal obligations - an unprecedented event in American history.

However, contrary to your July 23 account, this was not an unprecedented event.

The unprecedented event had raised alarm bells for China's top leaders.

It was an unprecedented event, the only time a newly promoted side had won the title in their first season.