Even harder to gauge was what it would take for the disaffected to say enough is enough and begin challenging their regime openly, defiantly, and in concert.

Because the financial crisis has lowered greenhouse gas emissions, the 20 reduction target set before the crisis is no longer challenging enough to catalyze a structural shift in the European economy.

A bit more challenging, right?

A bit more challenging, right? (Laughter)

But striking the proper balance is challenging.

That will be particularly challenging for Bernanke.

That is an assumption that needs challenging.

Emerging and challenging issues deriving from implementation

Finally, Japan s external environment today is more challenging.

However, the situation in Cité Soleil remains challenging.

Enough is enough.

Enough is enough.

Two serious problems make reconciliation in Afghanistan particularly challenging.

But success in Cairo might prove even more challenging.

This means that Europe probably faces another challenging year.

The selection of indicators has proven to be challenging.

Women challenging these norms are punished by violent means.

Emerging and challenging issues deriving from implementation and necessary

When Enough is Not Enough

Enough is not enough anymore.

The year ahead will be challenging and rife with uncertainty.

Everything we do, we believe in challenging the status quo.

You can see the trapezoids are a little challenging there.

Fortunately, such a way immensely challenging but nonetheless feasible exists.

This category is especially useful for solving especially challenging problems.

In this challenging environment, administrative infrastructures have continued to function.

This has been particularly challenging in remote and insecure areas.

These have indeed been very challenging times for our Organization.

America, however, is not alone in challenging Al Jazeera head on.

Aside from clarity, it is important that group goals be challenging.

The Second Great Awakening was challenging women's traditional roles in religion.

Determining an optimal level of accountability for results is also challenging.

Some individuals and entities have filed multiple lawsuits challenging their listing.

Some local journalists and civil society groups are challenging the credibility of some of the results, and the CPC is challenging the outcome of the presidential vote at the INEC.

I will say it again, Enough is enough.

Opposition leaders do not like the subject, but they avoid challenging it.

Most should be able to grow strongly, despite the challenging global environment.

Of these three imperatives, sustainability may be the most complex and challenging.

It will be challenging, but maybe also healthy for our common future.

The journey from 2011 to now has been challenging, exciting and tedious.

Managing such a large and complex peacekeeping mission was a challenging task.

If you're creative enough, playful enough, fun enough, can you get through to anybody? Yes or no?

It is time we all say, Enough is enough!

And this is a very challenging idea. It's a very challenging idea to mainstream media. It's a very challenging idea to anyone who has invested an enormous amount of time and expertise, and who has a lot of energy invested in the notion that he or she knows better than everyone else.

Enough!